Fresh from Columbia University College of Physicians and Surgeons in May of 1917, Theodore H. Sweetser, Sr. was commissioned as lieutenant in the U.S. Medical Officers-section Reserve Corps, U.S. Army, and soon attached to the 29th Division of the British Army fighting in the Third Battle of Ypres, Belgium. On reporting for duty on the battle front he found himself in the midst of fierce battle, one that claimed nearly 500,000 casualties on both sides. He stayed at the front tending the wounded and sick of both armies for nearly a year, all the while working while shells burst around him. He was awarded the British Military Cross for “Conspicuous Gallantry” during a gas attack. For relief he played cribbage and found other diversions with fellow officers. His diaries and letters from May to August, 1917, before leaving for the front, provide insights into his relationship with his family, giving context to the subsequent letters from the war zone. He was a native of Minneapolis, Minnesota, and practiced medicine there for nearly 50 years.