I decided to look up military branches on Ngram to determine if increased use of the terms correlate with war in the United States and if a certain branch was more popular during which war. I did this by tracking “army”, “navy”, “marines”, “air force”, and “military” in American English only.
It is obvious that the army is by far the most discussed branch. “Military” follows closely behind “army” and eventually passes “army” to become the most common term among the five in modern language. In the distance is the navy and then (once invented) the air force. Most people seem to use “military” as a general term to describe all the branches which explains why it has grown in popularity over the past 40 years. Also, “army” could be the most popular term for so long because it was the most common used military branch in the past due to the lack of advanced technology.
Also, the spikes in the term usage correlate with wars in America. The huge peak in 1776 was when the United States gained their independence, which also explains the peak in the navy because of the magnitude of overseas warfare. The peak in 1812-1816 correlates with the War of 1812. There was little to no peak in “navy” in 1865, though there was a peak in the other terms because of the Civil War’s lack of necessity for a navy. The peak in 1918 associates with World War I while in 1944 World War II was in full swing. There are some peaks that are more difficult to find correlations for. This could be because there were wars abroad that made people think of the military more. Since the terms all peaked during wars, it seems as if people were extremely preoccupied with the war and that the topic dominated conversations.