Kwajalein consists of a group of 90 coral islets that surround the third largest lagoon in the world. The total land area is 6.2 square miles and the atoll is 78 miles long. The islets of Kwajalein and Roi-Namur were the first of the Marshall Islands captured by U.S. troops in World War II. The atoll serves as a seaport, air stop and U.S. military missile testing site.