BERLIN • Dr Angela Merkel's would-be successor is gambling that one of Germany's riskier Cabinet jobs will help get her chances of becoming chancellor back on track.

In an unexpected about-face, Ms Annegret Kramp-Karrenbauer has taken command of Germany's military as defence minister.

It is a position that has ended several political careers in the past, though her predecessor, Dr Ursula von der Leyen, just landed the job of leading the European Commission in Brussels.

Ms Kramp-Karrenbauer, known as AKK in Berlin, had previously said she would steer clear of Dr Merkel's Cabinet, preferring to distance herself from a coalition government that is fraying at the seams.

Instead, she would build her case to replace Dr Merkel after the next election, due in 2021, from her position as leader of the Christian Democratic Union (CDU). But Ms Kramp-Karrenbauer has struggled to boost the fortunes of the CDU since taking charge in December. She fumbled with overtures to the party's right wing and saw a slide in the polls.

As of May, Dr Merkel had grown more determined to stay in office amid doubts that Ms Kramp-Karrenbauer was up to the job, according to party officials close to the Chancellor.

By opting to take over the fighting forces, Ms Kramp-Karrenbauer exchanges her independence for a position that could be the ultimate proving ground for her abilities.

When Dr von der Leyen took over in 2013, she herself was tipped as a potential chancellor.

After almost six years in the post, she has been mired in accusations about Germany's military readiness, with helicopters that cannot fly, submarines that cannot sail, and an investigation into her use of outside consultants. The call to Brussels got her out of a fix.

With about two years left in Dr Merkel's fourth term, Ms Kramp-Karrenbauer may manage to avoid some of the pitfalls of the Defence Ministry. But she will have to navigate deteriorating transatlantic relations.

BLOOMBERG