When his three-year term of service expired, Ellis received an honorable discharge, but after six months of civilian life he re-enlisted.

Sent to France as a private in Company C, 28th Infantry, 1st Division, he saw front-line action for 200 days near Soissons and was awarded the Silver Star.

The official record of the War Department states: He showed unusual courage in carrying supplies and in attacking strong points at Brouil, Pleissy, and Berney-le-Sac.

Our allies, recognizing Sergeant Ellis' bravery, awarded him the Chevalier Legion of Honor of France, and the Croix de Guerre with Palm, the Cross of War of Italy, Cross of War of Poland and Recognition by the Moroccan Government, two medals, Senior and Junior.On October 5, 1918, Ellis' division was participating in the Hundred Days Offensive near Exermont in northeast France.

In August 1919, he returned to St. Louis, where General John J. Pershing presented him with the Medal of Honor for his actions near Exermont.

Citation: During the entire day's engagement Sergeant Ellis operated far in advance of the first wave of his company, voluntarily undertaking most dangerous missions and single-handedly attacking and reducing machinegun nests.