Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Passage: At the time of the attack on Pearl Harbor, Yamagumo, under the command of Lieutenant Commander Yasuji Koga, was flagship of the 3rd Special Attack Force in the invasion of the Philippines, covering landings at Camiguin Island and Lingayen. However, on 31 December, she suffered severe damage after striking a Japanese naval mine. She was towed to Hong Kong for repairs in early February, and then limped to Yokosuka Naval Arsenal by 7 April. She remained under repair until 15 May 1942 but remained based at Yokosuka through the end of August 1942. She made one escort mission to Saipan at the end of December 1942. In February 1943, while attempting to escort Tatsuta Maru to Truk, she was unable to prevent the former luxury liner from being torpedoed by the submarine with the loss of 1,400 lives just east-southeast of Mikurajima.
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.

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