While Poland has relatively few women in uniform, compared to other countries in Europe, the Poles do actually recruit women for SOF (Special Operations Forces). The number actually in SOF units isn't clear (the Poles have some 300 active SOF commandoes). The Poles - who apparently were doing this even under the Communist regime - believe women can contribute to SOF ops in a number of ways. Most notably because, as women, they are "invisible" in many societies, and can go places, conduct surveillance, and so forth, in situations where men would be spotted immediately. The Poles have also discovered that a well trained female operator is as deadly as her male counterparts.
The Poles are not the only country to recruit women for their SOF units. The American Delta Force and British SAS (and many other nations) are believed to have women on board. Since these organizations tend to keep even the identities of their members secret, they don't want to reveal gender either. Elite outfits like SAS and Delta also do a lot of undercover and espionage work, and the last thing they want is the identities of their female operators revealed.
The CIA, MI-6 (British overseas spies) and similar organizations in other countries have long used women. During World War II, female agents were used a lot, even in some of the nasty, physical operations. The women acquitted themselves well. Thus after the war, there was less resistance to getting women involved with elite commando and espionage organizations. However, with all the secrecy these outfits employ, the story of the female operators has been lost, or at least ignored. There are actually several generations of these female operators out there now. So somewhere in the world, someone has a grandmother who, in her early days, had a license to kill.