Generate a correct and concise answer for the question based on the words in the context.
Q: Context : M. Waldo Hatler (January 6, 1894 - August 31, 1967) was a Sergeant in the United States Army during World War I who received the Medal of Honor for heroism near Pouilly, France, November 8, 1918.
Question : In what war was M. Waldo Hatler a combatant?
A:
World War I