An attack by the United States on a Nato ally would mean the end of both the military alliance and “post-second world war security”, Denmark’s leader has warned, after Donald Trump threatened again to take over Greenland. Fresh from his military operation in Venezuela, the US president said on Sunday the US needed Greenland “very badly” – renewing fears of a US invasion of the largely autonomous island, which is a former Danish colony and remains part of the Danish kingdom. Greenland’s foreign and security policy continues to be controlled by Copenhagen. Mette Frederiksen, the Danish prime minister, warned on...