OTTAWA – Allies around the world have promised to increase their help to Canada in its fight against hundreds of blazes that have swept through the country in its worst-ever start to wildfire season. Forest fires that have gathered strength over the last month have forced tens of thousands of people from their homes and sent a smoky haze billowing over a large swath of the United States. The fires have impacted mining operations in Canada and disrupted flights in the United States. On Thursday the Toronto District School Board, Canada’s largest, rescheduled or moved indoors all outside activities, including field trips and local school events. Although wildfires are common in Canada, it is unusual for blazes to be burning simultaneously in the east and west, stretching firefighting resources, forcing the government to send in the military to help, and fueling concerns about the worsening consequences of climate change.