President Donald Trump’s proposed tariff on imported steel and aluminum, at 25 percent and 10 percent, is much more than a shot across the bow. Indeed, this could be the official kickoff of the trade war we all anticipated. The protectionist trade policy, announced last week as the president met with metals executives, raised fresh inflation worries and had an immediate impact on capital markets.

As expected, the winners were domestic steelmakers. AK Steel (AKS), the only manufacturer in North America that produces carbon, stainless and electrical steels, rose as much as 9.5 percent Thursday.

AK Steel CEO Roger Newport praised Trump’s decision, saying he fully supports “the actions he plans to take to stem the tide of unfairly traded steel imports that threaten the national security of our country.”

Newport wasn’t alone. Drew Wilcox, vice president of steel giant Nucor (NUE), called the tariffs “a clear message to foreign competitors that dumping steel products into our market will no longer be tolerated.”

Among the biggest losers from the news were automakers, which account for a little more than a quarter of steel demand in the U.S., according to the American Iron and Steel Institute (AISI). That makes the industry the second-largest consumer following construction. Ford, General Motors, and Fiat Chrysler all fell more than 2 percent Thursday, and losses extended into Friday.

Get Ready for Higher Consumer Prices

To be clear, this is a huge deal, with serious inflationary implications. The U.S. is the world’s largest steel importer, so it’s very possible we could see retaliation from multiple trading partners on exports ranging from Florida orange juice to Kentucky bourbon to Wisconsin cheese. It’s hard to imagine a scenario where this is not passed on to consumers.

Trump was reportedly advised to exempt select allies, but it appears he’s chosen a no-exemptions option. Canada, the top supplier of steel and aluminum to the U.S., was spared in 2002 when former President George W. Bush imposed tariffs as high as 30 percent on steel.