Ellis Island
During and immediately following World War II, Ellis Island was used to hold German merchant mariners and "enemy aliens"—Axis nationals detained for fear of spying, sabotage, and other fifth column activity. In December 1941, Ellis Island held 279 Japanese, 248 Germans, and 81 Italians removed from the East Coast. Unlike other wartime immigration detention stations, Ellis Island was designated as a permanent holding facility and was used to hold foreign nationals throughout the war. A total of 7,000 Germans, Italians and Japanese would be ultimately detained at Ellis Island. It was also a processing center for returning sick or wounded U.S. soldiers, and a Coast Guard training base. Ellis Island still managed to process tens of thousands of immigrants per year during this time, but many fewer than the hundreds of thousands per year who arrived before the war. After the war, immigration rapidly returned to earlier levels.
Amphibious warfare
Not knowing which of the many islands would be the American target, the Japanese would have to disperse their strength by garrisoning many islands that would never be attacked. An island like Eniwetok in the Marshall Islands, would, Ellis estimated, require two regiments, or 4,000 Marines. Guided by Marine observer aircraft, and supplemented by Marine light bombers, warships would provide enough firepower so that Marines would not need any heavy artillery (in contrast to the Army, which relied heavily on its artillery). Shelling defended islands was a new mission for warships. The Ellis model was officially endorsed in 1927 by the Joint Board of the Army and Navy (a forerunner of the Joint Chiefs of Staff).