Amid a growing trade war with one of the United States’ closest allies, President Donald Trump on Thursday moved to rename Lake Ontario to “Lake America,” needling Canada further after trade talks collapsed.

Trump’s executive order marks the president’s latest attempt to use rebranding as an assertion of power — after signing an order to rename the Gulf of Mexico on his first day back in office.

Trump has wide latitude over how the US government refers to geographic landmarks, but he can’t force other countries to follow suit. Here’s what to know:

Trump had been floating the name change since trade talks between the US and Canada fell apart last week.

The president enacted 50% tariffs on roughly $20 billion worth of Canadian goods over the weekend, and Canada quickly followed suit by announcing increased tariffs on various US products. Trump has threatened to further escalate if Canada doesn’t back down, though talks seem to be on hold for now.