WWI Aviator MacLeish was appointed ensign in the Naval Reserve Flying Corps August 31, 1917. MacLeish was the son of an immigrant from Scotland and the lineage on his mother's Hillard side was traced to Elder Brewster, the minister aboard the Mayflower. He was the brother of Pulitzer Prize-winning poet Archibald MacLeish, and like his brother "Archie", he attended Yale College. A member of the class of 1918, he left college to serve in the war. The young officer wrote home constantly with letters showing the youthful enthusiasm then subsequent weariness of combat that is characteristic of men at war. In France he participated in many raids over the enemy's lines before he was transferred in September 1918 to Eastleigh, England. On October 14, 1918, which was just weeks before the end of the war, he was in a successful raid with the Royal Air Force. This time his plane was shot down by eight German fighters forcing him to crash-land. No one could say how he died, but evidence proved MacLeish survived the initial crash. His was found dead not far from the crash site three months later by a Belgian farmer. Before the burial, a photograph of the wreckage with the body in a flooded field was sent to brother "Archie", who had also seen action in France. Kenneth MacLeish was Naval Aviator #74 flying with RAF 213 Squadron, and he was posthumously awarded the Navy Cross for "distinguished service and extraordinary heroism". Later the destroyer USS MacLeish (DD-220) was named for him.

Archie wrote about his brother:

FORTUNE AND MEN'S EYES
This other's afterward -
after the Armistice, I mean, the floods,
the weeks without a word. That foundered
farmyard is in Belgium somewhere.
The faceless figure on its back, the helmet buckled, wears what looks like Navy wings. A lengthed shadow falls across the muck about its feet...