Short answers, pulled from the story.
The Japanese 25th Army invaded Malaya from Indochina by amphibious assault on the 8th of December 1941. This attack occurred virtually simultaneously with the attack on Pearl Harbor which precipitated United States entry into the war.
Over a period of 15 hours starting at 23:00 on the 8th of February 1942, Yamashita's heavy guns fired a bombardment of 88,000 shells along the straits to cut telephone lines and isolate forward units. Shortly before 20:30 on the 8th of February, the first wave of Japanese troops from the 5th Division and 18th Division began crossing the Johor Strait to attack the 22nd Australian Brigade.
A British lieutenant acting as an envoy with a white flag was killed with a bayonet after approaching Japanese forces who had broken through near Alexandra Barracks Hospital. After troops entered the hospital they killed up to 50 soldiers including some undergoing surgery and also killed doctors and nurses.
Percival formally surrendered shortly after 17:15 on the 15th of February 1942 after meeting with Yamashita at Ford Motor Factory. Under terms hostilities ceased at 20:30 that evening following his decision to surrender rather than attempt a counter-attack.
Since 1998 Singapore has observed Total Defence Day on the 15th of February each year marking the anniversary of the surrender. Yearly observances include memorial service held at War Memorial Park since 1967 to recognize civilians who lost lives during occupation.