The second factor ignored is the historical one. In the past century, there have been many attempts to form female infantry units. All failed. Women did fight, as female American MPs did, as light infantry. These were usually irregular fighters, often guerillas. Here, the experience was similar to that of female American army MPs. But you cant win wars with lightly armed irregulars.
The third factor is that the vast majority of military women dont want to be in the infantry. Opinion surveys have shown that. The main source of female troops eager to serve in the infantry are career female officers who know that the highest ranks in the army are only open to officers who have served in combat units.
A recent firefight in Iraq, where a female MP NCO led the defense of a convoy, which killed or wounded over half the 40 or so attackers, is being pushed as proof that women should be allowed to serve in the infantry. Currently, the U.S. Army does not allow women to serve in infantry, armor or artillery units. The media coverage of this issue nearly always misses the key reasons for not having women in these units. First, there are the purely physical reasons. Infantry combat is intensely physical, involving carrying heavy loads quickly, often under fire. The problem with this has been that women are not built for carrying those kinds of loads, particularly under those conditions. Armor and artillery jobs also involve the muscle issue. Many operational and maintenance tasks in armor and artillery units involve a lot of physical strength.
Women have been successful warriors for thousands of years, but in much smaller numbers than men. With the invention of lightweight firearms, women overcame the muscle disadvantage. When fighting was done with sword, spear and bow, men were much more lethal versus women because of greater size and strength. But when both had rifles or pistols, it was just a matter of training and motivation. But modern combat involves more than just the individual soldiers weapons, but lots of stuff to drag around for a long time.
Getting women into combat units has become an article of faith, not fact, for many people. It shouldnt be. Such willful ignorance gets people killed.