Trump’s move to impose new tariffs has bewildered the United States’ closest allies and trading partners, who have vowed to respond with levies of their own.

Trump has long proposed raising tariffs—or taxes on imported goods that the businesses importing them pay the U.S. government—before the election, and said in November he’ll impose a 25% tariff rate on all imports from Mexico and Canada on the first day of his presidency and will impose an additional 10% tariff rate on all imports from China on top of other tariffs.

Amid warnings of price increases, Canada moved quickly to retaliate, China said it had planned countermeasures and Mexico said it would soon unveil its response.