Donald Trump campaigned on a pledge to put 'America first'. In his first year in office the policy was pursued in a number of areas including immigration and national security, but, when it came to the economy, despite threats, the status quo more or less remained the same. Now that's changed. President Trump has signed an order imposing a 25 percent tariff on steel and a 10 percent tariff on aluminium imports. So will the move rebuild and protect the US steel industry, as the president has pledged? Will it result in a trade war? And is American economic nationalism pushing its closest trading partners away from the US - towards free trade with each other? (Photo: Getty Images)