Donald Trump is slamming former Defense Secretary James Mattis as the 'world's most overrated general' after the official published a scalding op-ed denouncing the president's leadership. Mattis finally broke his silence following his exit from the White House and blasted Trump as a 'mockery of the Constitution' in a fiery statement shared Wednesday. He even compared Trump's divisive tactics to those of the Nazis, and noted that U.S. troops found unity in their strength. 'Probably the only thing Barack Obama & I have in common is that we both had the honor of firing Jim Mattis, the world's most overrated General. I asked for his letter of resignation, & felt great about it,' Trump tweeted Wednesday evening. While Trump claimed that he fired Mattis, the general had submitted his resignation in December 2018 after he disagreed with Trump's decision to pull US forces out of Syria.