When I came to this country in 1970, The US Steel was the largest steel manufacturing company in the world.  Then due to lenient and ill-advised policies in this country in the 80s, slowly and slowly manufacturing base started deteriorating and shifted to overseas.  I believe, for any country, a strong manufacturing base is must for its prosperity and security.  This country imports lot of steel from China who is subsidizing its steel industry and dump steel in the United States at a very competitive price.  We have kind of become complacent about the supply of steel from China.  God forbids if there is a war between China and the US, this supply will disappear which means, the US can run into a scenario of shortage of steel to manufacture defense armaments - fighter jets, tanks, missiles etc.  So, from country's security standpoint, self-sufficiency in steel and aluminum manufacturing is must.  Needless to say, these tariffs will create jobs too - more jobs means higher GDP, higher revenue for the exchequer and higher standard of living for the people living here.