Less so for the last several decades than any time in the past, due to the establishment of first as hoc (e.g., ICTY) and then standing (i.e., ICC) tribunals not directly tied to a particular belligerent's military.
But, yes, that's still an issue, particularly with the US electing not to ratify the Rome Statute.
Worth noting that I've been reading a lot about the UK's involvement in Iraq and Afghanistan recently and have started reading "The Wrong Enemy" about the US involvement in Afghanistan:
NB I'm certainly not one for prosecuting low level individuals (i.e. the forces actually on the ground) apart from exceptional circumstances (e.g. the Royal Marine who was caught on camera executing a wounded person) but I do have a lot of anger directed at the political and military leaderships in the UK.
e.g. Curtis LeMay stated that he thought that had the US lost the war with Japan "he fully expected to be tried for war crimes."
https://en.wikipedia.org/wiki/Curtis_LeMay