It heavily depends on which army you are joining and what cause they fight for. Joining army can be step towards supporting atrocities and it can be step towards preventing them.
Just like with joining police - in some places it is good thing to do. In others, you are joining another criminal organization.
Yeah, there was no difference between joining SS and resistance or American army. Or, between fighting against invading army (like Russia) and being invader.
Soldiers from both sides in every conflict will commit war crimes, including horrible war crimes. That's the grim reality and you can either accept it or put on propaganda blinders. Modern war is hell.
And yet, sone armies commit way more of them then others.
Some armies habe those attrocities as mandates, it is their job to commit genocide. Others don't. In some armies you have to participate in others don't.
It is just not true that it would all be the same. Complete pacifism is just enabling the biggest genocides that go on while congratulating yourself.
"We're invading to defend the people against a brutal oppressor" is the argument always used. By Americans in WWII, by Russia today. Some of the worst war crimes and genocides in history have been committed systematically by the armies you've so far mentioned: Germany, America and Russia. These atrocities have been ordered from the highest leadership in these nations. Modern war is hell and there are no good guys left when it's over. If you believe that, they are recruiting volunteers.
Americans did not happened to be the invading brutal oppressor commiting genocide in WWII. Their standard behavior during that time was was remarkably better then behavior of Soviet army which was better then behavior of German army.
Your position is that joining Jewish resistance is as bad as joining SS and both are totally the same as being member of an American army.
Just like with joining police - in some places it is good thing to do. In others, you are joining another criminal organization.