President Donald Trump on Monday announced by tweet that he had fired his defence secretary Mark Esper, further destabilizing a government already navigating Trump’s refusal to concede election defeat to Democrat Joe Biden. “Mark Esper has been terminated. I would like to thank him for his service,” Trump said on Twitter, announcing his replacement by Christopher Miller, the current head of the National Counterterrorism Center. Mark Esper who had clashed with Trump over his suggestion of using military personnel to quash civic unrest had prepared a letter of resignation,...