Pistorius, 65, has been tasked with building up Germany's long underfunded armed forces and supporting Kyiv with defence goods since Russia launched its full-scale invasion of Ukraine over three years ago.

Known for his straight talk, good humour and commitment to the troops, he has often been voted Germany's most popular politician in opinion polls, at a time of growing unease about the threat posed by a hostile Russia.

Pistorius is also known for his strong support of Ukraine in the face of Russia's three-year invasion.

Merz, the long-time rival of his party's former chancellor Angela Merkel will take the helm of Europe's top economy at a time when US President Donald Trump has rattled transatlantic ties and Europe is in a tense standoff with Russia.