Why push Mattis out on Jan 1st? Could it be because he is going to face court martial?
https://www.whitehouse.gov/presidential-actions/2018-amendments-manual-courts-martial-united-states/
Sec. 3. (a) Pursuant to section 5542 of the Military
Justice Act of 2016 (MJA), division E of the National Defense Authorization Act for Fiscal Year 2017, Public Law 114-328, 130 Stat. 2000, 2967 (2016), except as otherwise provided by the MJA or this order, the MJA shall take effect on January 1, 2019.
(b) Nothing in the MJA shall be construed to make punishable any act done or omitted prior to January 1, 2019, that was not punishable when done or omitted.
(c) Nothing in title LX of the MJA shall be construed to invalidate the prosecution of any offense committed before January 1, 2019. The maximum punishment for an offense committed before January 1, 2019, shall not exceed the maximum punishment in effect at the time of the commission of such offense.