I am going to have to focus this a lot more.
Here are some potentially helpful resources through TCL:
Global Books In Print (though it may return way too many search results)
Children's Literature Comprehensive Database (which I am very comfortable with!)
Books and Authors (pretty self-explanatory)
Wilson Core Collections
One way that I could focus in is by looking at the war books that have won awards in the past 60 years. By narrowing in on the Caldecott winners, I am guaranteed to get picture books... plus it might be interesting how many of the selections are about war.
This website lists the books without description so I can just look up these titles in World Cat (which was the best source to check out the descriptions in compared to Amazon & Children's Literature Comprehensive Database)
Just to see if this would be a good gauge- I looked up the titles for 50-53 and found one pertaining to war (called America's Ethan Allen- a biography of the patriot and soldier who led the Green Mountain Boys in the capture of Fort Ticonderoga from the British in 1775).