Christmas is a day of sombre remembrance for veterans of the World War II battle of Hong Kong, which fell to the Japanese on this day 70 years ago after 18 days of desperate fighting. Hopelessly outnumbered and outgunned, allied troops from Britain, Canada, Hong Kong and India fought to defend the former British colony from Japanese forces which had attacked from mainland China on December 8, 1941. The assault came a day after Japan landed what it hoped would be a killer blow on the United States at Pearl Harbour. By the time Hong Kong Governor Sir Mark Young surrendered on what became known as "Black Christmas", around 4,000 soldiers from both sides had been killed in the battle. But instead of bringing peace to the island, the surrender began almost four years of brutal Japanese occupation in which allied prisoners were tortured and abused, local villages razed and women raped on a large scale. Hong Kong Ex-Servicemen's Association vice chairman Kenny Yau, a former British army captain, said about 20 veterans from the Hong Kong infantry and artillery units who fought to defend their city were still alive. "They just want world peace 70 years on," he said. "They wanted an apology from Japan a long time ago but as they have aged and their memories fade, I haven't heard them discuss that for a while." Not so the Canadians, who held an emotional wreath-laying ceremony at Hong Kong's Sai Wan War Cemetery earlier this month to mark the start of the battle. Hong Kong was the first action for Canadian infantry in World War II. After the commemorative ceremony, Canadian Veterans Affairs Minister Steven Blaney and a delegation of veterans travelled to Japan to accept a formal apology for their treatment in captivity. Blaney called the apology a "crucial step in ongoing reconciliation and a significant milestone in the lives of all prisoners of war". "It acknowledges their suffering while honouring their sacrifices and courage," he said in a statement released this month. The intensity of the fighting and the Japanese soldiers' combat skills took many of the British-led defenders by surprise. Canadian Sergeant Major John Robert Osborn was posthumously awarded the Victoria Cross, the Commonwealth's highest medal for bravery, after throwing himself on a Japanese grenade to save his men on December 19th. In the same action, Brigadier John K. Lawson became the most senior Canadian officer to be killed in action in World War II when he left his besieged headquarters to "shoot it out", according to official records. About 290 Canadians were among the roughly 2,100 allied troops killed in the battle. Hundreds of survivors endured years of abuse and starvation as prisoners of war, leading to more than 260 additional Canadian deaths. Yau described Japan's apology to the Canadians as "a good sign". But he added: "They should have apologised a long time ago". In a strange coincidence, Hong Kong police on Thursday detonated seven World War II-era grenades found near a popular hiking trail on the south of the island, where some of the most intense hand-to-hand fighting took place. Two British M36 grenades and five Japanese Type 91 grenades were discovered near the Wilson Trail between Stanley and Repulse Bay, a key route over the mountainous hump dividing Hong Kong between north and south. Hong Kong's Museum of Coastal Defence is showing a photographic exhibition saluting the territory's Canadian defenders to mark the battle's 70th anniversary. "As many Canadians fought to the last man, and the gallantry of the soldiers deserves special mention, this pictorial exhibition pays tribute to the Canadian troops who defended Hong Kong," a government statement said.