Appellee Robert C. Ballard is a lieutenant in the United States Navy. After more than nine years of active service as a commissioned officer, he failed, for a second time, to be selected for promotion to the grade of lieutenant commander, and was therefore subject to mandatory discharge under 10 U.S.C. § 6382(a).1 He brought suit in federal court claiming that if he had been a woman officer, he would have been subject to a different separation statute, 10 U.S.C. § 6401, under which he would have been entitled to 13 years of commissioned service before a mandatory discharge for want of promotion.2 He claimed that the application of § 6382 to him, when compared with the treatment of women officers subject to § 6401, was an unconstitutional discrimination based on sex in violation of the Due Process Clause of the Fifth Amendment.3

The District Judge issued a temporary restraining order prohibiting Ballard's discharge. Subsequently, a three-judge District Court was convened to hear the claim pursuant to 28 U.S.C. §§ 2282, 2284. After hearings upon motions by the Government defendants, that court issued a preliminary injunction against Ballard's discharge. 350 F.Supp. 167. Thereafter, the case came before the three-judge court for decision on the merits. Relying upon Frontiero v. Richardson, 411 U.S. 677, 93 S.Ct. 1764, 36 L.Ed.2d 583, and concluding that the challenged mandatory-discharge provisions are supported solely by considerations of fiscal and administrative policy, the court held that § 6382 is unconstitutional because the 13-year tenure provision of § 6401 discriminates in favor of women without sufficient justification. 360 F.Supp. 643. Accordingly, the court enjoined the Navy from discharging Ballard for failure to be promoted to the grade of lieutenant commander before the expiration of 13 years of commissioned service. Id., at 648. We noted probable jurisdiction of this appeal from that injunctive order. 415 U.S. 912, 94 S.Ct. 1405, 39 L.Ed.2d 465. See 28 U.S.C. § 1253.

* At the base of the system governing the promotion and attrition of male line officers on the Navy is a congressional designation of the authorized number of the Navy's enlisted personnel, 10 U.S.C. § 5401, and a correlative limitation upon the number of active line officers as a percentage of that figure. 10 U.S.C. § 5403.4 Congress has also established the ratio of distribution of line officers in the several grades above lieutenant in fixed proportions to the total number of line officers. §§ 5442, 5447(a).

The Secretary of the Navy is required periodically to convene selection boards to consider and recommend for promotion male line officers in each of the separate ranks, § 5701, and must provide the boards so convened with the number of male line officers that may be recommended for promotion to the next higher grade. § 5756. Eligible officers are then recommended for promotion by the selection boards, based upon merit, and are placed on a promotion list and promoted in due course as vacancies occur in the higher ranks. § 5769. Because the number of lieutenant commanders is set by statute, the number of lieutenants, like Ballard, who may be recommended for promotion and placed on a promotion list in any year depends upon the number of vacancies existing and estimated for the coming year in the rank of lieutenant commander. § 5756.

Wholly separate promotion lines are established for the various categories of officers. Thus, in addition to the selection boards that are convened to review the promotion of male line officers, different selection boards are convened to recommend for promotion staff corps officers (except for women officers appointed under § 5590), § 5702, male officers in the Marine Corps, § 5703, and women line officers, § 5704(a), and women staff officers who are appointed under § 5590. § 5704(b). The convening of these separate selection boards permits naval officers within each category to be considered for promotion in comparison with other officers with similar opportunities and experience.

Because the Navy has a pyramidal organizational structure, fewer officers are needed at each higher rank than are needed in the rank below. In the absence of some mandatory attrition of naval officers, the result would be stagnation of promotion of younger officers and disincentive to naval service. If the officers who failed to be promoted remained in the service, the promotion of younger officers through the ranks would be retarded. Accordingly, a basic 'up or out' philosophy was developed to maintain effective leadership by heightening competition for the higher ranks while providing junior officers with incentive and opportunity for promotion. It is for this reason, and not merely because of administrative or fiscal policy considerations, that § 6382(a) requires that lieutenants be discharged when they are 'considered as having failed of selection for promotion to the grade of lieutenant commander . .. for the second time.'5 Similar selection-out rules apply to officers in different ranks who are twice passed over for promotion.6

The phrase 'failed of selection for promotion' in § 6382(a) is a statutory term of art. It does not embrace all eligible officers who have been considered and not selected for promotion. Before an officer is considered to have failed of selection for the first time, he must have been placed within a 'promotion zone' established by the Secretary of the Navy. The Secretary each year establishes 'promotion zones' of officers who will either be selected for promotion to the next higher grade or who will be considered to have failed of selection for promotion for the first time. See §§ 5764, 5776. The number of officers in the zones, established for each grade, is set at a level to ensure a flow of promotions consistent with the appropriate terms of service in each grade, see § 5768, and to provide opportunity for promotion of others in succeeding years. The number of officers within each zone is thus based on 'a consideration of the number of vacancies estimated for the next higher grade in each of the next five years, the number of officers who will be eligible for selection in each of those years, and the terms of service that those officers will have completed.' § 5764(a).

Section 6401 is the mandatory-attrition provision that applies to women officers appointed under § 5590, including all women line officers and most women officers in the Staff Corps.7 It provides for mandatory discharge of a woman officer appointed under § 5590 when she 'is not on a promotion list'8 and 'has completed 13 years of active commissioned service in the Navy.' § 6401. Section 6401 was initially intended approximately to equate the length of service of women officers before mandatory discharge for want of promotion with that of male lieutenants discharged under § 6382(a).9 Subsequently, however, Congress specifically recognized that the provisions of § 6401 would probably result in longer tenure for women lieutenants than for male lieutenants under § 6382. When it enacted legislation eliminating many of the former restrictions on women officers' participation in the naval service in 1967,10 Congress expressly left undisturbed the 13-year tenure provision of § 6401. And both the House and the Senate Reports observed that the attrition provisions governing women line officers would parallel 'present provisions with respect to male officers except that the discharge of male officers probably occurs about 2 years earlier.' S.Rep.No. 676, 90th Cong., 1st Sess., 12; U.S.Code Cong. & Admin.News 1967, p. 1850; H.R.Rep.No.216, 90th Cong., 1st Sess., 17 (emphasis added).11

It is against this background that we must decide whether, agreeably to the Due Process Clause of the Fifth Amendment, the Congress may accord to women naval officers a 13-year tenure of commissioned service under § 6401 before mandatory discharge for want of promotion, while requiring under § 6382(a) the mandatory discharge of male lieutenants who have been twice passed over for promotion but who, like Ballard, may have had less than 13 years of commissioned service. In arguing that Congress has acted unconstitutionally, appellee relies primarily upon the Court's recent decisions in Frontiero v. Richardson, 411 U.S. 677, 93 S.Ct. 1764, 36 L.Ed.2d 583, and Reed v. Reed, 404 U.S. 71, 92 S.Ct. 251, 30 L.Ed.2d 225.

In Frontiero the Court was concerned with 'the right of a female member of the uniformed services to claim her spouse as a 'dependent' for the purposes of obtaining increased quarters allowances and medical and dental benefits under 37 U.S.C. §§ 401, 403, and 10 U.S.C. §§ 1072, 1076, on an equal footing with male members.' 411 U.S., at 678, 93 S.Ct., at 1766. Under the governing statutes, a serviceman could automatically claim his spouse as a 'dependent,' but a servicewoman's male spouse was not considered to be a 'dependent' unless he was shown in fact to be dependent upon his wife for more than one-half of his support. The challenged classification was based exclusively on gender, and the Government conceded that the different treatment of men and women service members was based solely upon considerations of administrative convenience. The Court found this disparity of treatment constitutionally invalid. In the words of the plurality opinion:

'(A)ny statutory scheme which draws a sharp line between the sexes, solely for the purpose of achieving administrative convenience, necessarily commands 'dissimilar treatment for men and women who are . . . similarly situated,' and therefore involves the 'very kind of arbitrary legislative choice forbidden by the (Constitution) . . ..' Reed v. Reed, 404 U.S., at 77, 76, 92 S.Ct. at 254. We therefore conclude that, by according differential treatment to male and female members of the uniformed services for the sole purpose of achieving administrative convenience, the challenged statutes violate the Due Process Clause of the Fifth Amendment insofar as they require a female member to prove the dependency of her husband.' Id., at 690—691, 93 S.Ct., at 1772.

The case of Reed v. Reed, supra, involved quite similar considerations. In that case the Court considered the constitutionality of an Idaho probate code provision that, in establishing who would administer a decedent's estate, gave a 'mandatory' preference to men over women when they were in the same degree of relationship to the decedent. The Idaho law permitted no consideration of the individual qualifications of particular men or women as potential administrators, but simply preferred males in order to reduce probate expenses by eliminating contests over the relative qualifications of men and women otherwise similarly situated. The Court held that '(b)y providing dissimilar treatment for men and women who are thus similarly situated, the challenged section violates the Equal Protection Clause.' 404 U.S., at 77, 92 S.Ct., at 254.

In both Reed and Frontiero the challenged classifications based on sex were premised on overbroad generalizations that could not be tolerated under the Constitution. In Reed, the assumption underlying the Idaho statute was that men would generally be better estate administrators than women. In Frontiero, the assumption underlying the Federal Armed Services benefit statutes was that female spouses of servicemen would normally be dependent upon their husbands, while male spouses of servicewomen would not.

In contrast, the different treatment of men and women naval officers under §§ 6382 and 6401 reflects, not archaic and overbroad generalizations, but, instead, the demonstrable fact that male and female line officers in the Navy are not similarly situated with respect to opportunities for professional service. Appellee has not challenged the current restrictions on women officers' participation in combat and in most sea duty. Specifically 'women may not be assigned to duty in aircraft that are engaged in combat missions nor may they be assigned to duty on vessels of the Navy other than hospital ships and transports.' 10 U.S.C. § 6015. Thus, in competing for promotion, female lieutenants will not generally have compiled records of seagoing service comparable to those of male lieutenants. In enacting and retaining § 6401, Congress may thus quite rationally have believed that women line officers had less opportunity for promotion than did their male counterparts, and that a longer period of tenure for women officers would, therefore, be consistent with the goal to provide women officers with 'fair and equitable career advancement programs.' H.R.Rep. No. 216, supra, at 5. Cf. Kahn v. Shevin, 416 U.S. 351, 94 S.Ct. 1734, 40 L.Ed.2d 189.12

The complete rationality of this legislative classification is underscored by the fact that in corps where male and female lieutenants are similarly situated, Congress has not differentiated between them with respect to tenure. Thus women staff officers not appointed under § 5590 are subject to the same mandatory attrition rule of § 6382(a) as are male officers. These include officers in the Medical, Dental, Judge Advocate General's, and Medical Service Corps. See 10 U.S.C. §§ 5574, 5578, 5578a, 5579. Conversely, active male lieutenants who are members of the Nurse Corps, like female lieutenants in that Corps, are within the ambit of 10 U.S.C. § 6396(c), which contains a 13-year tenure provision like § 6401.

In both Reed and Frontiero the reason asserted to justify the challenged gender-based classifications was administrative convenience, and that alone. Here, on the contrary, the operation of the statutes in question results in a flow of promotions commensurate with the Navy's current needs and serves to motivate qualified commissioned officers to so conduct themselves that they may realistically look forward to higher levels of command. This Court has recognized that 'it is the primary business of armies and navies to fight or be ready to fight wars should the occasion arise.' U.S. ex rel. Toth v. Quarles, 350 U.S. 11, 17, 76 S.Ct. 1, 5, 100 L.Ed. 8. See also Orloff v. Willoughby, 345 U.S. 83, 94, 73 S.Ct. 534, 540, 97 L.Ed. 842. The responsibility for determining how best our Armed Forces shall attend to that business rests with Congress, see U.S.Const., Art. I, § 8, cls. 12—14, and with the President. See U.S.Const., Art. II, § 2, cl. 1. We cannot say that, in exercising its broad constitutional power here, Congress has violated the Due Process Clause of the Fifth Amendment.13

The judgment is reversed.

Mr. Justice BRENNAN, with whom Mr. Justice DOUGLAS and Mr. Justice MARSHALL join, dissenting.

The Court concludes that the statutory scheme which results in different periods of tenure for male and female line lieutenants of the Navy does not contravene the Due Process Clause of the Fifth Amendment because 'Congress may . . . quite rationally have believed that women line officers has less opportunity for promotion than did their male counterparts, and that a longer period of tenure for women officers would, therefore, be consistent with the goal to provide women officers with 'fair and equitable career advancement programs." Ante, at 508. I believe, however, that a legislative classification that is premised solely upon gender must be subjected to close judicial scrutiny. Frontiero v. Richardson, 411 U.S. 677, 93 S.Ct. 1764, 36 L.Ed.2d 583 (1973), Kahn v. Shevin, 416 U.S. 351, 94 S.Ct. 1734, 40 L.Ed.2d 189 (1974) (Brennan, J., dissenting). Such suspect classifications can be sustained only if the Government demonstrates that the classification serves compelling interests that cannot be otherwise achieved. Here, the Government as much as concedes that the gender-based distinctions in separation provisions for Navy officers fulfill no compelling purpose.

Further, the Court goes far to conjure up a legislative purpose which may have underlain the gender-based distinction here attacked. I find nothing in the statutory scheme or the legislative history to support the supposition that Congress intended, by assuring women but not men line lieutenants in the Navy a 13-year tenure, to compensate women for other forms of disadvantage visited upon them by the Navy.1 Thus, the genderbased classification of which appellee complains is not related, rationally or otherwise, to any legitimate legislative purpose fairly to be inferred from the statutory scheme or its history, and cannot be sustained.

* As the Court recounts, § 6401 was enacted as part of the Women's Armed Services Integration Act of 1948, 62 Stat. 368. This Act, while providing for the first time a permanent role for women in the military, severely limited their career opportunities. Among other things, it provided that women in the Navy could not be permanently promoted above the rank of commander, and it set the number of women lieutenants, lieutenant commanders, and commanders at a small percentage of the number of regular women officers on active duty. Perhaps because these limitations upon promotion opportunities made it impractical to guarantee women line officers promotion at any uniform rate, the promotion zone system provided for men by the Officer Personnel Act of 1947, 61 Stat. 860, was not applied to them. And, as explained by the Court, without a promotion zone system, the basis for determining involuntary separation under § 6382(a), whether an officer has twice 'failed of selection for promotion,' has no meaning.2 Therefore, the separation provisions for women line officers, given the rest of the statutory provisions applicable to them, had to be pegged to time served rather than to opportunities for promotion. The number of years selected for women line lieutenants, 13, corresponded exactly to the normal number of years Congress intended to precede separation for a male officer not chosen for promotion. See ante, at 504—505 n. 9.3 Thus, Congress' original purpose in enacting slightly different separation provisions for men and women is quite certain—to create the same tenure in years for women lieutenants as for the average male lieutenant before involuntary separation was permitted.

However, for reasons not entirely clear upon the record in this case, the promotion zone system for men did not, as administered by the Navy, result in the normal 13-year tenure for men before involuntary separation contemplated by §§ 5764 and 5768.4 Rather, in 1967 the normal tenure for men seems to have been about 11 years, see H.R.Rep.no. 216, 90th Cong., 1st Sess., 17; S.Rep.No.676, 90th Cong., 1st Sess., 12; and in 1972, when respondent was due for discharge, it was eight or nine years. Brief for Appellants 16.

In 1967, Congress decided to eliminate many of the provisions restricting career opportunities for women. In doing so it wishes, as the Court notes, to provide women with 'fair and equitable career advancement programs.' H.R.Rep.No.216, supra, at 5. However, contrary to the Court's assumption, Congress determined to achieve this goal, not by providing special compensatory treatment for women, but by removing most of the restrictions upon them and then subjecting them to the same provisions generally governing men. Id., at 3; S.Rep.No.676, supra, at 2, U.S.Code Cong. & Admin.News 1967, p. 1839.

First, the entire structure of the 1967 Act is directed toward assimilating as much as possible the promotion structure for women line officers to that of men. The Act, for example, provided for a promotion zone system for women line officers in the Navy, 10 U.S.C. § 5764(d), and applied the 'failure of selection' designation to women by amending 10 U.S.C. § 5776.5 These additions make the retention of 13-year tenure for women line lieutenants somewhat anomalous, since the 'failure of selection' designation appears to have no function except as an aid to determining involuntary separation. Thus, as the hesitant language the Court uses in describing Congress' possible compensatory purpose recognizes, it is impossible to divine from the structure of the Act itself a reason for retaining the 13-year tenure for women but not for men.

Second, the legislative history of the 1967 Act makes quite clear that Congress' purpose in retaining the 13-year tenure for women line lieutenants was not to take account of the limited opportunities available to women in the Navy. Congress explicitly recognized that in some instances involuntary retirement and separation provisions 'permit women to remain on active duty for longer periods than male officers.' It believed that '(u)nder current circumstances, there is no logical basis for these differences.' S.Rep.No.676, supra, at 2, U.S.Code Cong. & Admin.News 1967, p. 1840. (Emphasis supplied.) See H.R.Rep.No. 216, supra, at 2—3; Hearing on H.R. 4772, 4903, 5894, before the Senate Committee on Armed Services, 90th Cong., 1st Sess., 41 (1967). The 1967 Act was to 'apply the standard attrition provisions of male officers promotion and retirement laws to women officers. The only exception to this would be the selective continuation of nurses.' H.R.Rep.No. 216, supra, at 3.6 (Emphasis supplied.) See S.Rep.No.676, supra, at 2. In light of these statements, Congress could not have had the purpose of compensating women line officers for their inferior position in the Navy by retaining longer tenure periods for women.

Moreover, the legislative history is replete with indications of a decision not to give women any special advantage. 'The purpose of the legislation has been limited to the removal of arbitrary restrictions. No effort has been made to provide special assurances to women officers, and none is recommended.' Letter from General Counsel, Department of Defense, in S.Rep.No.676, supra, at 5, U.S.Code Cong. & Admin.News 1967, p. 1842; H.R.Rep.No.216, supra, at 9. 'The purpose of the bill is to create parity only in respect to recognizing merit and performance.' Id., at 7. See S.Rep.No.676, supra, at 3.7 (Emphasis supplied.) To infer a determination purposely to perpetuate a longer retention period for women line officers is, therefore, eitirely to misconceive Congress' perception of the problem and of the proper solution. While the reason for the failure to revise §§ 6382 and 6401 is not clear, it is certainly plausible to conclude that Congress continued to believe, as it had in 1948, that the separation provisions for men and women would, given the opportunity to work properly, result in equal average tenure for both sexes.8

Given this analysis of the relationship between § 6382 and § 6401, the difference in tenure which resulted in fact from the operation of these sections manifestly serves no overriding or compelling governmental interest. Indeed, the appellants concede as much in discussing proposed H.R. 12405 (93d Cong., 2d Sess.), §§ 2(5) and 4(18), to which the Court refers, ante, at 510, n. 13: 'The Department of Defense considers that the separate rule for women, while serving a legitimate governmental purpose . . . is on balance no longer needed as a matter of military personnel policy.' Brief for Appellants 18. (Emphasis supplied.) Since the executive department most intimately concerned with the promotion policy in the Navy can perceive no need for the gender-based classification under attack, the interest served by the classification, if any, can hardly be overriding or compelling.9

Further, while I believe that 'providing special benefits for a needy segment of society long the victim of purposeful discrimination and neglect' can serve 'the compelling . . . interest of achieving equality for such groups,' Kahn v. Shevin, 416 U.S. at 358—359, 94 S.Ct., at 1739 (Brennan, J., dissenting), I could not sustain this statutory scheme even if I accepted the Court's supposition that such a purpose lay behind this classification. Contrary to the Court's intimation, ante, at 508, women do not compete directly with men for promotion in the Navy. Rather, selection boards for women are separately convened, 10 U.S.C. § 5704, the number of women officers to be selected for promotion is separately determined, 10 U.S.C. § 5760, promotion zones for women are separately designated, 10 U.S.C. § 5764, and women's fitness for promotion is judged as compared to other women, 10 U.S.C. § 5707. In this situation, it is hard to see how women are disadvantaged in their opportunity for promotion by the fact that their duties in the Navy are limited, or how increasing their tenure before separation for nonpromotion is necessary to compensate for other disadvantages.

The Court suggests no purpose other than compensation for disadvantages of women which might justify this gender-based classification. I agree that the 'up or out' philosophy 'was developed to maintain effective leadership by heightening competition for the higher ranks while providing junior officers with incentive and opportunity for promotion.' Ante, at 502—503. But the purpose behind the 'up or out' philosophy applies as well to women as to men. The issue here is not whether the treatment accorded either women or men under the statutory scheme would, if applied evenhandedly to both sexes, forward a legitimate or compelling state interest, but whether the differences in the provisions applicable to men and women can be justified by a governmental purpose.10

For this same reason, the invocation of the deference due Congress in determining how best to assure the readiness of our Armed Forces for battle cannot settle the issue before us. As Frontiero v. Richardson, 411 U.S. 677, 93 S.Ct. 1764, 36 L.Ed.2d 583 (1973), illustrates, the fact that an equal protection claim arises from statutes concerning military personnel policy does not itself mandate deference to the congressional determination, at least if the sex-based classification is not itself relevant to and justified by the military purposes.

Thus, the validity of the statutory scheme must stand or fall upon the Court's asserted compensatory goal. Yet, as the analysis in Part I, supra, demonstrates, this purpose was not in fact behind either the original enactment of § 6401 or its retention in 1967. While we have in the past exercised our imaginations to conceive of possible rational justifications for statutory classifications, see McGowan v. Maryland, 366 U.S. 420, 425—428, 81 S.Ct. 1101, 1104—1106, 6 L.Ed.2d 393 (1961), we have recently declined to manufacture justifications in order to save an apparently invalid statutory classification. Cf. James v. Strange, 407 U.S. 128, 92 S.Ct. 2027, 32 L.Ed.2d 600 (1972); Weber v. Aetna Casualty & Surety Co., 406 U.S. 164, 92 S.Ct. 1400, 31 L.Ed.2d 768 (1972). Moreover, we have analyzed asserted governmental interests to determine whether they were in fact the legislative purpose of a statutory classification, Eisenstadt v. Baird, 405 U.S. 438, 442 443, 92 S.Ct. 1029, 1032—1033, 31 L.Ed.2d 349 (1972), and have limited our inquiry to the legislature's stated purposes when these purposes are clearly set out in the statute or its legislative history. Johnson v. Robison, 415 U.S. 361, 376, 94 S.Ct. 1160, 1170, 39 L.Ed.2d 389 (1974). Never, to my knowledge, have we endeavored to sustain a statute upon a supposition about the legislature's purpose in enacting it when the asserted justification can be shown conclusively not to have underlain the classification in any way.11

Since the Government here has advanced no governmental interest fairly to be gleaned from §§ 6382 and 6401 or their history which can justify this gender-based classification, I would affirm the judgment below.

Mr. Justice WHITE, dissenting.

Agreeing for the most part with Mr. Justice BRENNAN's dissenting opinion, I also dissent from the judgment of the Court.