sentences:  The harbour was later transformed into an important port in the northeast of the island, as quarry and timber from the neighbouring Johor and Pulau Ubin became lucrative.Access to the harbour from the city was primarily via Serangoon Road.In World War II, the British and Allied troops mistakenly believed that the Imperial Japanese Army would invade Singapore by crossing the Serangoon Harbour after the Japanese troops moved into and captured Pulau Ubin.