MORE OFTEN than not, debates over the Equal Rights Amendment have bogged down force the question of whether its ratification would force the Pentagon to use women in combat. The Defense Department has now made a move - on grounds that have nothing to with women's rights - that would pull the rug out from under that argument. It has asked Congress to lift the bars against the assignment of women to combat-related jobs and to ships at sea, replacing them with a law permitting the secretary of each armed service to decide where women should serve.

The problem the Defense Department is trying to solve is quite simple. It is having trouble recruiting enough well-qualified males to fill all the jobs in combat units, and it has a surplus of well-qualified female volunteers. Unless women can be assigned to a much broader range of military jobs, the department says, it will be forced either to leave slots in combat units unfilled or to fill them with less-qualified men. That is a powerful argument. It says, in effect, that we can have a first-rate military force if women are used to their full capabilities and a second-rate one if they aren't.

Much of the emotion that this issue has stirred in recent years arises out of an old-fashioned notion of what "combat" is. Every time it is discussed, the picture is drawn of women in foxholes or trenches, struggling with mortars and other heavy equipment. Many women - and some men - are physically unfit for such jobs, and we doubt that any secretary of the army would ever assign them there. But sitting in a missile silo or flying a bomber or operating a piece of navigational equipment can be just as much a part of combat. We, at least, would rather have a well-qualified woman in a critical combat job than an unqualified man.

In addition to this nmed of the armed services to upgrade their personnel is the need of women who choose to make a career out of the military service to have access to those jobs. They are, in many instances, the key to career advancement. If the armed forces are to have a female component - and the nation decided to decades ago that they should have - the jobs necessary to advancement must be open to the women who help compose them. Other wise,. the quality of female volunteers will dimnish over time, and then the squeeze for well-qualified personnel will really be on. It is a happy coincidence that the Pentagon has realized its own practical need to open the jobs available to women at the same time the women in the military are seeking those jobs for a quite different reason. Congress ought to change the law as the Defense Department has requested - and without the slightest hesitation.