Artillery in Action

Plywood, semi-interlocking, cut along color lines with 6 figure pieces.  Leaving Brown U. early in 1917 to join the army, my father was trained on "big guns" (his words) and sent to France as part of the rapid expansion of the American Expeditionary Force.  The last photo on a small camera he took with him shows him standing in a French boxcar as his unit was brought up to the front to engage the Germans.  The armistice was declared before he was injured or killed.  Thus, this puzzle has special meaning to me which is why I was willing to replace the 4 missing pieces in such a small puzzle.