Choose the word which is different from the rest.

The answer is D. Montgomery.

A. Nimitz was an American admiral who served as the Commander in Chief of the U.S. Pacific Fleet during World War II.
B. Yamamoto was a Japanese admiral who was the commander-in-chief of the Combined Fleet during World War II.
C. Nelson was a British admiral who served as First Lord of the Admiralty during the Napoleonic Wars.
D. Montgomery was a British field marshal who served as the Allied commander-in-chief in North Africa and Western Europe during World War II.

The difference between Montgomery and the other three is that Montgomery was not a naval commander.