At the end, Penny Johnson says she followed her husband's movements on a map. During World War II, people in the military had it drilled into them that they could not say anything about where they were in letters sent back home, and to make sure they kept that rule, the mail from soldiers was censored. This has been mentioned in numerous histories of World War II. With Clark Gable being an officer, it's even less likely any information about his movements around Europe would have been available to his wife.
When Dr. Johnson and Snapshot are trapped behind German lines during the Battle of the Bulge, Snapshot asks if they should try to go towards Cologne (Germany). At this stage of the war, December 1944, the Allies had not yet crossed into Germany, except in one or two places, and only in toehold positions.
During surgery, only one of the nurses (or doctor) has her mask up over her nose (to minimize the chance of any of the patients catching an airborne infection from the medical personnel).
(at around 1h 2mins) Dr. Johnson is examining a chest X-ray. However, the X-ray is reversed on the view-box (i.e., it's backward).