Semper Fi by W.E.B. Griffin is the first in the series of books on The Corps. The Preface provides the background to events in China, beginning in the 1900s with the Boxer Rebellion. The problem is settled with the Protocol of 1901 which places troops of the foreign powers in China. This means the U.S. troops are in Shanghai, Peking and other places. Navy gunboats patrol the Yangtze River. By 1941, the lines are drawn for World War II in China. The Japanese take over the Russian interests and are determined to expel foreigners from China.

As the first in the series, the book takes place before the United States is involved in World War II. It introduces many of the characters that appear in later books in the series.

The main characters in Semper Fi is Ken McCoy. He is a China Marine and stationed in Shanghai as the book opens. When he is attacked by four Italian Marines, he kills two of them. Captain Banning is assigned to defend him, but the charges are dropped.

They decide to get McCoy out of Shanghai for a while and send him on a convoy to Peking. Banning has Lieutenant John Macklin looking for information on the Japanese and tells McCoy that he is just along for the ride. When the convoy returns to Shanghai, Macklin has found out nothing and has been caught by the Japanese. McCoy has found out a great deal of information about Japanese troop movements by visiting a brothel. When the Italians learn that McCoy is back in Shanghai, they have a Welcome Home, Killer McCoy party. This is how McCoy comes to be nicknamed Killer.

Banning is impressed with McCoy and sends him on another convoy assignment on which he is able to take pictures. The Marine brass is impressed with the photos and sends Captain Ed Sessions to learn more information. Sessions poses as a missionary with Reverend and Mrs. Feller. There is an incident during which eighteen coolies are killed. After this, McCoy is sent back to the United States. Macklin is caught falsifying reports, trying to blame McCoy for his and Sessions' being caught by the Japanese. Banning writes a bad efficiency report for Macklin and has him sent back to the States.

Macklin causes more problems for McCoy at Quantico and almost causes him to be eliminated from the Platoon Leader's Course, but both McCoy and Pick Pickering graduate and go to other assignments.

Semper Fi is "must" reading for W.E.B. Griffin fans. It sets the stage for the rest of the books in The Corps series. The book is quick and easy reading and well worth the reader's time.