Given the task definition and input, reply with output. In this task, you're given a context, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both context and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the context or linked information.

Context: She made one escort mission to Saipan at the end of December 1942. Link Information: In 1914, during World War I, the island was captured by the Empire of Japan. The Empire was awarded formal control of the island in 1919 by the League of Nations as a part of its mandated territory of Nanyo. Militarily and economically, Saipan was one of the most important islands in Nanyo and became the center of subsequent Japanese settlement. Immigration began in the 1920s by ethnic Japanese, Koreans, Taiwanese and Okinawans, who developed large-scale sugar plantations. The Nanyo Kohatsu Kabushiki Kaisha built sugar refineries, and under Japanese rule, extensive infrastructure development occurred, including the construction of port facilities, waterworks, power stations, paved roads and schools, along with entertainment facilities and Shinto shrines. By October 1943, Saipan had a civilian population of 29,348 Japanese settlers and 3,926 Chamorro and Caroline Islanders.

Answer: the Empire of Japan.
Which country had control over Saipan when Yamagumo arrived as an escort?