The appointment follows the resignation of Christine Lambrecht at a crucial time for the ministry, with Germany under intense pressure to send battle tanks to Ukraine.

Pistorius, 62, who is a member of Scholz's Social Democrats (SPD) and interior minister of Lower Saxony state, is a surprise choice for the post.

Much better-known politicians had been thought to be in the running, such as Eva Hoegl, the parliamentary commissioner on the armed forces, and Labour Minister Hubertus Heil.

But the chancellor insisted Pistorius was the right man for the job at a time when Germany is looking to overhaul and revive its armed forces in response to Russia's invasion of Ukraine.

Scholz called Pistorius "an extremely experienced politician" who "has been involved in security policy for years and, with his competence, assertiveness and big heart, is exactly the right person to lead the Bundeswehr (armed forces) through this era of change".

- Military overhaul -

Pistorius himself said he found the appointment "very surprising".

However, he pledged to do his utmost to tackle the "new situation that has arisen with the Russian attack on Ukraine".

"The troops can rely on me to be there for them whenever necessary. I want to make the Bundeswehr strong for the time that lies ahead of us," he said.

The appointment, which will officially take effect on Thursday, ends a streak of three female defence ministers, and upends a promise by Scholz when he became chancellor in 2021 to keep his cabinet gender-balanced.

Pistorius has a huge task ahead of him at a time of sweeping change for the Bundeswehr and just as Germany faces a crunch moment in its policy towards the conflict in Ukraine.

The Ukraine Defence Contact Group, which coordinates arms supplies to Kyiv, is due to meet at the Ramstein Air Base in Germany on Friday.

Germany has repeatedly come under fire since the start of the war for dithering over which weapons to send to Ukraine, and is currently under pressure from Kyiv to agree to supply battle tanks.

Russia's invasion prompted Scholz to announce a drastic overhaul of the military after years of chronic underinvestment -- something that Pistorius will now have to oversee.

- 'Strong leader' -

The chancellor pledged to raise military spending to two percent of GDP and to revive the ailing army with a special fund of 100 billion euros ($108 billion).

But Lambrecht, appointed as defence minister in the chancellor's first cabinet, had committed a series of gaffes and was eventually seen as not up to the task.

Patience for the minister finally ran out when she posted a widely ridiculed New Year's video on social media in which she lauded her "special experiences" as defence minister in 2022 against a backdrop of loud fireworks.

The resulting media uproar finally led Lambrecht to announce her resignation on Monday.

Marie-Agnes Strack-Zimmermann, who heads the parliamentary defence commission, said Pistorius was someone who "knows the issue of security and how to work with those who are committed to our security".

"He will be judged in Berlin on whether he understands the needs of the troops and is assertive in representing them at the chancellery and the defence ministry," she told the Rheinische Post newspaper.

Hoegl, who herself worked closely with Pistorius during a stint specialising in interior and legal affairs in the Bundestag lower house of parliament, also welcomed the appointment.

"With Boris Pistorius, the troops are getting a committed, strong leader and passionate politician in difficult times," she told the Rheinische Post.