Whatever you may say or think about Donald Trump, he is slowly but surely trying to tick off the campaign promises he made.
One of the big ones was jobs. He promised to bring back work to the decaying steel towns across America's rust belt where factories are closing and whole areas are blighted by unemployment, poverty and drugs.
Since 2000, 50,000 jobs have been lost in the steel industry and 40,000 in the aluminium factories.
As a consequence the US is the world's largest importer of steel, bringing in nearly four times as much as it exports, according to the White House.
The US imported five times as much primary aluminium as it produced in 2016.
:: Trump tariffs order risks world trade war
Donald Trump thinks a pretty severe dose of protectionism is one way of putting that right.
The tariffs – 25% on steel and 10% on aluminium – will take effect in two weeks' time and will be across the board.
But, significantly, there will be exemptions and the main grounds for them will be national security.
So countries like Canada and Australia and the EU may well be able to apply for waivers on the basis of an ongoing military relationship.
That is the theory, at least. How it works in practice is quite another matter.
And there remains huge potential for a trade war that, like all wars, will be easy to start but less easy to end.
The Chinese are the exporters in Mr Trump's gunsights.
Although technically they are only responsible for about 5% of America's steel imports, it is actually far greater than that because of what are called trans-shipments.
Chinese steel ends up in third party countries and is shipped to America under a different flag. But it is still Chinese steel. The Chinese are threatening reprisals and it could get very messy.
The EU is also threatening to hit back-slapping tariffs on American imports such as jeans, bourbon whisky, Harley Davidson motorcycles and peanut butter.
And a trade war may be just one consequence of this decision.
With these sweeping tariffs, Donald Trump has already spooked the markets, upset friends and foes alike, his top economic adviser has quit and there is a rift with fellow Republicans
In at least one sense it is a bargaining chip; a move designed to win America a better deal in the North America Free Trade Agreement.
The President has been explicit in saying that if he gets the deal he wants on NAFTA then Canada and Mexico will be spared the tariffs. It is a pretty crude strategy but will probably work.
More from Donald Trump
"If you don't have steel, you don't have a country," said Donald Trump before signing the proclamations on the tariffs.
He promised he would do something and now he has. What is less certain is how much damage it could do to world trade… and even possibly to America.
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Sky News
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