Good morning. After threatening tariffs because of wildfire smoke, the U.S. did impose levies, but for a different reason altogether. More on that below, along with fire strategy intentions and dark matter discoveries.

U.S. President Donald Trump is escalating his trade war against Canada, imposing 50-per-cent tariffs on a range of goods to hit back at Ottawa for retaliating against his previous tariffs.

In a surprise move on Monday, Mr. Trump signed three proclamations invoking Section 338 of the Depression-era Tariff Act, which has never previously been used, to impose the levies on Canada in response to the country curbing imports of U.S. autos, alcohol and dairy.

In addition to tariffing Canadian alcohol and dairy products, the President’s new levies will also hit a grab bag of hundreds of other goods, ranging from hockey sticks to cement to electronic equipment to Christmas ornaments.

The tariffs take effect on Aug. 19 and will not include an exemption for goods trading under the U.S.-Mexico-Canada Agreement, broadening the economic damage Mr. Trump has been trying to inflict on one of his country’s closest allies since he returned to office last year.

U.S. Trade Representative Jamieson Greer’s office said the tariffs would apply to nearly US$20-billion worth of Canadian goods, roughly five per cent of the country’s exports to the U.S.

Read the story for the full trade and economic picture.

While wildfires continued to move rapidly across northern Ontario, Premier Doug Ford said he plans to discuss the need for a national fire strategy with his fellow premiers and Prime Minister Mark Carney when they meet in Prince Edward Island this week.

The context: Canada is one of the few G7 countries that does not have a stand-alone federal emergency management agency. In June, a key recommendation of a Senate Committee report urged creating a federal co-ordinating office for wildfires and emergency response, modelled after existing organizations in the U.S., Australia, Japan and the U.K.

On the ground: Ontario NDP MPP Lise Vaugeois, who represents the riding of Thunder Bay–Superior North, said the government has not done enough to prepare for wildfires. “Climate change is changing everything,” she said. “They have ignored what they’ve been told needs to be done for years.”

Explained: Here’s an overview of the current situation, in maps and charts.

Yemen’s Iran-aligned Houthis said they would impose a naval blockade on Saudi Arabia, potentially creating a new front against the United States in its war with Iran. Tehran had been pressing the Houthis to close the Bab el-Mandeb gateway to the Red Sea if the U.S. continued to attack its power infrastructure. President Donald Trump defended the latest strikes on Iran as honouring the deaths of American service members in recent Iranian attacks.

The energy threat: The full closure of the Bab el-Mandeb strait would reduce global oil supply by 7 per cent, raising the threat to global energy supplies and trade beyond the Gulf. After the closure of the Strait of Hormuz, Bab el-Mandeb had been providing a lifeline for the energy market, helping to keep down global oil prices.

Enbridge Inc. has started construction on the $4-billion expansion of its pipeline system for transporting natural gas in British Columbia, with Ottawa touting the economic spinoffs from Canada’s energy industry.

The context: In April, the federal government approved the Sunrise expansion program, which will increase capacity by 17 per cent at Enbridge’s T-South system, focusing on southern B.C. but also bolstering the U.S. Pacific Northwest.