The Canadian government says it has begun its largest search ever for the lost ships of a doomed 1845 quest for the Northwest Passage. The ships of Sir John Franklin\'s expedition, Erebus and Terror, disappeared almost 170 years ago in the Arctic waters off what is now Nunavut. Both ships became trapped in ice off King William Island, and Franklin and his entire crew of 129 men took to the ice where they all eventually perished. The search for Franklin\'s ships has another significance beyond the history, as Canadian officials have often cited the importance of this search in terms of asserting Canada\'s northern sovereignty, Canadian Broadcasting Corp. News reported Thursday. John Geiger, co-author of a 2004 book that probed the fate of the Franklin\'s failed 19th-century polar mission, agrees the Franklin search suggest more than simply an interest in finding two old ships. \"There\'s absolutely an agenda,\" Geiger, now the editorial board editor of the Globe and Mail newspaper, said. \"I can\'t imagine a government investing the kind of resources, scarce resources, in pursuit of historical knowledge. The government wants \"to assert Canadian sovereignty over the Arctic islands and also the waterways,\" Geiger says. \"A Franklin ship located in the Northwest Passage is a relatively minor piece of legal ammunition,\" she says, but it is also \"probably the most valuable cultural, historical, international-scale material\" that a Canadian government can point to in asserting a claim for greater control over the Northwest Passage. As climate change is opening up the North to more foreign vessels, Canada has a vested interest in claiming control, experts said.