Secretary of Defense Jim Mattis issued a farewell letter Monday morning to all Department of Defense employees as his time in the Department draws to an end.

In the letter, Mattis, who will turn defense secretary duties over to current Deputy Secretary of Defense Patrick Shanahan before ringing in the new year, instructs DoD personnel to "keep the faith in our country and hold fast, alongside our allies, aligned against our foes.”

The highly respected former Marine Corps general announced his resignation as secretary of defense Dec. 20, a noteworthy decision in that it came just one day after President Donald Trump ordered U.S. forces to be pulled out of Syria.

In his resignation letter, Mattis wrote that America must maintain “strong alliances” and show “respect to those allies," before citing the “Defeat-ISIS coalition of 74 nations” as proof of what such alliances can accomplish.

Mattis intended to stay on until Feb. 28 to allow the president ample time to find “a secretary of defense whose views are better aligned with yours," he wrote, but just days after the resignation letter was circulated, President Trump announced he was pushing Mattis out early, with Shanahan assuming acting secretary duties Jan. 1.

Mattis' farewell letter to DoD personnel offers steadying advice amid looming uncertainty over troop numbers in Syria and Afghanistan.

“Let nothing which is transpiring, change, hinder, or delay your military movements, or plans," he wrote, quoting a telegram President Abraham Lincoln sent to Gen. Ulysses S. Grant in February 1865.

“Our Department’s leadership, civilian and military, remains in the best possible hands," he continued. “I am confident that each of you remains undistracted from our sworn mission to support and defend the Constitution while protecting our way of life. Our Department is proven to be at its best when the times are most difficult.”

Mattis has been highly regarded by both Republicans and Democrats as secretary of defense, but no demographic has held CHAOS in as favorable a light as the military, a group he addressed in his final sign-off.

“It has been my high honor to serve at your side," he wrote. "May God hold you safe in the air, on land, and at sea.”

Read the full letter below.

A farewell letter to all DoD employees from outgoing Secretary of Defense Jim Mattis. (Department of Defense)
A farewell letter to all DoD employees from outgoing Secretary of Defense Jim Mattis. (Department of Defense)