I found his wartime cartoons to be of the standard-issue anti-war kind as found in leftist publications such as The Masses. The post-war cartoons I noticed while Googling seemed to be mostly gentle in tone, such as might be found in American general-interest magazines of that time. (Though I easily could have missed harsher ones that failed to pop up during my search.)
Below are examples of van der Hem's painting and illustration. He was versatile, and had a nice touch better suited to illustration than Fine Arts painting.
This was included in David Apatoff's blog post.
Apparently van der Hem spent some time in Spain.
This might have been painted after 1930.