Upon his return from Europe at the end of the First World War, Lang enlisted in the United States Navy. Lang served for most of his navy career in the China Fleet, where he was quartermaster in the ship's company of several gunboats. In the 1920s, he was awarded the US Navy Cross and the Japanese Order of the Chrysanthemum for his heroism during a combined Japanese/US naval operation on the Yangtze River against Chinese warlord forces. The Chinese had besieged the foreign diplomatic legations on the river.