Japanese Occupation (1942–1945)

Sultan Ibrahim became a personal friend of Tokugawa Yoshichika during the 1920s. Tokugawa was a scion of the Tokugawa clan, and his ancestors were military leaders (shōgun in Japanese) which ruled Japan from the 16th to the 19th centuries. When the Japanese invaded Malaya, Tokugawa accompanied General Yamashita Tomoyuki's troops and was warmly received by Sultan Ibrahim when they reached Johor Bahru at the end of January 1942.

Yamashita and his officers then stationed themselves at Istana Bukit Serene and the state secretariat building, Sultan Ibrahim Building to plan for the invasion of Singapore.^[2][3] From the palace, he had a splendid view of the positions of the Australian Army and Navy across the Straits of Johor. Yamashita used the palace tower as viewing point as it had a bird's eye view of Singapore.

Although advised by his top military personnel that the palace was an easy target, Yamashita was confident that the British Army would not attack Istana Bukit Serene because it was the pride and possession of the Sultan of Johor. Yamashita's prediction was correct as the British Army did not dare attack the palace.

Shortly before the Japanese surrendered in 1945, Sultan Ibrahim was expelled from his residence at Istana Bukit Serene and was forced to reside at Istana Pasir Pelangi, the crown prince's palace.^[4]