well my assumptions and this is based on what i think would make sense. currently its a dont ask dont tell policy. the military's official stance is they accept them but unofficially they are shunned and usually treated poorly and bullied. most of the time if its known they are gay, there are plenty of attempts to force them out through extra pressure.

i think in the case of a dire need for soldiers, it would be just like the civil war and the world wars where blacks werent really allowed to serve and those who did were only allowed in certain support positions. But, once the need for troops became great enough blacks were encouraged to serve, albeit in their own segregated units but the military laxed and brought them in because the need outweighed the opinions of those who were against it.

i think you would see the military become more open to gays serving, maybe not more hospitable or more friendly towards them, but more willing to look away just that much more because its one more body on the battlefield