German Defense Minister Ursula Von der Leyen on Friday asked the White House to provide “clarity” about next steps following the resignation of U.S. Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE.

“Because the United States has such a prominent role and responsibility in the global security architecture, it is important for everyone to quickly get clarity about succession and the future course,” she said in a statement to Reuters.

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President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE said Thursday that Mattis will leave the administration in February. The announcement was met with bipartisan concern on Capitol Hill; many lawmakers considered the former Marine Corps general a stabilizing force in the White House.

His eventual departure had long been expected following accounts of his disagreements with Trump and after the president suggested a Cabinet shakeup was imminent following November’s midterm elections.

Mattis is a staunch supporter of NATO, an international alliance that Trump has torched, claiming other member nations have failed to beef up their military spending.

“If we did not have NATO today, we would need to create it,” Mattis said in 2017.

Mattis acknowledged on Thursday that he and Trump have not seen eye to eye on a number of policies.

“Because you have the right to have a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position,” Mattis wrote in a resignation letter devoid of any praise for the commander in chief. “One core belief I have always held is that our strength as a nation is inextricably linked to the strength of our unique and comprehensive system of alliances and partnerships. While the US remains the indispensable nation in the free world, we cannot protect our interests or serve that role effectively without maintaining strong alliances and showing respect to those allies.”

Trump and German Chancellor Angela Merkel have feuded in the past over trade issues and a Russian gas pipeline that goes through Germany.