[8] In the 1920s and 30s Mactarian painted, made prints, and provided illustrations for periodicals and books, such as John Pfeiffer's popular Science in your Life.
[8] In 1939 he painted Cotton Growing, Manufacture, and Export, a striking (and still-extant) mural at the US Post Office in Dardanelle, Arkansas, for which he was paid $660 by the Treasury Department's Section of Fine Arts.
While in quarantine he learned of a $12,000 prize for a contest to paint a 12-by-50-foot mural in the new War Department Building in Washington, D.C.; company officers, impressed with his sketches, provided him with materials and a private workroom in the Men’s Service Club.
[11] He served with the 337th Engineer General Service Regiment, part of the US Fifth Army, in the Italian Campaign, reaching the rank of TEC3 (Sergeant).
Unlike many war artists, who depicted what they saw in a plain, illustrative style, Mactarian applied a Contemporary Realist approach to his paintings and drawings which at times bordered on Surrealism as they portrayed both the large-scale physical destruction of war and, particular to the Engineers, the striking incongruity of large geometric structures (such as pre-fabricated Bailey bridges, concrete bunkers, or gas pipelines) imposed on Italy's ancient landscapes.