As you allude to. There’s some elements that become quite regular components of war strips, but this due to the nature of war comics in general and not specific to Ennis.
I grew up reading Victor, Batlle and Commandos, I pretty much learned to read with them and obviously it was a popular genre in the UK comics scene (which was booming in he 70s and early 80s). So it’s a genre that I am fond of. Like you say, Ennis is the only guy really writing them any more, and having written probably close to 80-100 war strips by now if we count the arcs in Battlefields and War stories, I’m sure there are some similarities to found - just as there are with Jason Aaron’s superhero work or Ed Brubaker’s crime stories.
I’m sure if one wanted to be off hand enough, a straw man argument could be made for the superhero genre, crime genre, fanstasy genre and horror genre etc
I think the comment that once you have ‘read one Ennis war story you have read them all’ is needlessly reductive, bordering on dismissive towards a writer who is is absolutely meticulous in his research and brings so much to the comics industry by standing his ground and doing it his way. There’s no many writers out there who are in a position to do that.