When Canadian Prime Minister Justin Trudeau visited the White House in February, he and President Trump traded nothing but mutual compliments and smiles. And they never smiled bigger than when they discussed the issue of trade between the two countries.

"Having more jobs and trade, right here in North America, is better for the United States and is also much better for Canada," said Trump.

Trudeau replied, "Thirty-five U.S. states list Canada as their largest export market, and our economies benefit from the over $2 billion in two-way trade that takes place every single day. Millions of good, middle-class jobs on both sides of the border depend on this crucial partnership."

But since this moment of amity, Trump has apparently decided that Trudeau was not the Dudley Do-Right he seemed to be. All along, he'd been secretly making war on American jobs from deep within Canada's snowy forests.

Not a real war, of course, but trade war. Trump is upset that Canada has been letting its timber industries pay what he considers excessively low royalties to cut down Canadian trees. This means Canadian lumber companies can sell softwood for lower prices to American industries, a crime that makes the use of the word "bacon" to describe what is clearly just ham seem like a trivial matter in comparison.

Trump is standing up to this threat by imposing a retroactive, punitive 20 percent tariff on imports of Canadian softwood lumber. The wisdom of this is perhaps best demonstrated by the fact that Sen. Chuck Schumer, D-N.Y., thinks it's a good idea (which is to say, it isn't a good idea).

The U.S. logging industry that Trump and Commerce Secretary Wilbur Ross are trying to protect from competition employs 53,000 Americans. The construction industry, which prefers to buy wood at lower prices rather than higher ones, employs 7 million, and it is not the only industry that will be hurt by this tariff.

As with his move toward imposing new tariffs on steel, Trump is threatening to sacrifice the health of several large and growing industries in order to save a handful of jobs in one of America's smaller and shrinking industries.

The manufacturers of homes, furniture, flooring, siding, light frames and boats, among others, will be harmed by Trump's tariff on Canadian softwood. Thousands of the jobs will be lost in homebuilding alone. Homes will be up to 4 percent more expensive.

American makers of wooden finished goods will also suffer as their products become less competitive in both foreign and domestic markets as a result of the higher prices produced by this tariff.

This is not a recipe for putting America First, or for making it Great Again. Nor is it wise to poison the well when dealing with America's second-largest and most polite trading partner.