Trump tweets nomination of General Mark Milley for chairman of the Joint Chiefs of Staff, the nation's top military position

• President Donald Trump announced his nomination of General Mark Milley for the chairmen of the Joint Chiefs of Staff on Saturday.
• The nomination breaks an unofficial tradition of rotating chairmen by which service they align with.
• Trump was expected to make the nomination at the Army-Navy game Saturday afternoon.

President Donald Trump took to Twitter Saturday morning to announce his nomination of General Mark Milley, 60, as the new chairmen of the Joint Chiefs of Staff, that nation's top military position.

"I am pleased to announce my nomination of four-star General Mark Milley, Chief of Staff of the United States Army - as the Chairman of the Joint Chiefs of Staff, replacing General Joe Dunford, who will be retiring," wrote Trump.

Milley has served as chief of staff of the Army since August 2015.

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He reportedly graduated from Princeton before serving as a Green Beret. He would go on to hold leadership roles in the wars in Iraq and Afghanistan.

The selection of Milley breaks the unofficial tradition of rotating chairmen by which service they're a part of. Milley is replacing Dunford, a Marine, who took the reigns from an Army chairman.

The announcement comes surprisingly earlier, considering Dunford's official tenure doesn't end until Oct. 2019. Trump went on to tweet, "Date of transition to be determined."

Trump was expected to make the announcement at Saturday's Army-Navy game, reportedly telling White House pool reporters on Friday, "I have another one for tomorrow that I'm going to be announcing at the Army-Navy game, I can give you a little hint: It will have to do with the Joint Chiefs of Staff and succession."