In the summer of 1917, soon after the United States entered World War I, he became aide and flag secretary for Commander, Cruiser Force, Atlantic Fleet.

After serving in that capacity into the following winter, Bristol was awarded the Navy Cross for his service as flag secretary and acting chief of staff to Commander, Cruiser and Transport Force.

Bristol then commanded Breckinridge (DD-148) and Overton (DD-239) in succession, serving in the latter during that ship's operations in the Black Sea during the capitulation of White Russian forces to the Bolsheviks in November 1920.

Following a brief tour as aide for Commander, Scouting Fleet, he sailed to Rio de Janeiro, Brazil, to join the American naval mission there.

Reporting to the battleship Arizona (BB-39) in February 1927, Bristol served as executive officer of that dreadnought until April of the following year, and then moved to the Naval Air Station (NAS), San Diego, California, for aviation instruction.

He held this important position throughout the tense, undeclared war with Germany in the summer and autumn of 1941 and through America's entry into the global conflict on December 7, of that year.

Designated vice admiral on February 27, 1942, Bristol remained in that important command until he suffered a fatal heart attack at NS Argentia, Newfoundland, on April 27, 1942.