Trump 1.0 and his tumultuous relationships with National Security advisers -- 5 in that job over 4 years / 48 months

Beginning in January 2017

Trump told Michael Flynn, "You're Fired!"

and for 7 days brought in Keith Kellogg.

H.R. McMaster served that position

Feb. 2017 until April 2018;

Trump as well hired then fired 

John Bolton (hired April 2018, fired Sept. 2019);

also hired for the remainder of his 2017 - Jan. 2021 term:

Robert O'Brien (Sept. 2019 until Jan. 19, 2021

which was 13 days after the Jan. 6 attempted

insurrection)