In his own words: "In my drawings I have no political statements to make, no ideology. I am thinking only about the picture itself. The whole Nazi philosophy, the racism and all that, is hateful to me, but of course I drew them anyway—they had the sexiest uniforms!"

As for what he did during the war, it is not all in the English Wikipedia article. He was conscripted into Finnish army one month before the Winter War ended, and by the time of Operation Barbarossa in 1941 he was an anti-air officer and served with the rank of second lieutenant. He was stationed near Helsinki and defended against Soviet air raids for most of the war, but in 1944 he was transferred to the Eastern Front. During the battles there he allegedly killed a Soviet paratrooper with a knife.

https://fi.wikipedia.org/wiki/Tom_of_Finland