Should our country defend other NATO countries that maintain low military defense budgets relative to their GDP?

Should the U.K. defend other NATO countries that maintain low military defense budgets relative to their GDP?

The North Atlantic Treaty Organization (NATO) is an intergovernmental military alliance formed by 28 countries in 1949 after the Second World War. To join NATO each member country pledged to spend at least 2% of their GDP on military spending and defense and defend each other against threats from any non-member country. In a July 2016 interview with the New York Times Republican Presidential nominee Donald Trump suggested that the United States would not defend NATO member countries who had failed to increase their military budgets to above 2% of Gross Domestic Product. The suggestion defie…  s a pact made by NATO members when it was formed in WWII that they would defend each other against any attack by a non-member nation. France, Turkey, Germany, Canada, and Italy are countries that are currently spending less than 2% of their GDP on military defense.