In what year did General Jim Mattis resign?

General Jim Mattis resigned from his position as the Secretary of Defense in December 2018, with his resignation taking effect on January 1, 2019. This corresponds with a significant moment in U.S. military and political history, as his departure followed differences he had with President Donald Trump over various defense policies, particularly regarding the withdrawal of U.S. troops from Syria. This event marked a notable shift in defense leadership, as Mattis, a highly respected military figure known for his strategic acumen, had a profound impact on military operations during his tenure.

The correct choice reflects the accurate timeline of events concerning his resignation.