In a country long haunted by guilt over its role in World War II, the armed forces were for decades not seen as a priority and suffered from chronic underinvestment.

But Moscow's decision to send troops into Ukraine in February last year prompted a dramatic shift in Berlin, which has pledged huge sums to boost the military to combat growing threats.

Releasing the first set of new policy guidelines for the Bundeswehr, or armed forces, since 2011, Defence Minister Boris Pistorius said that with Russian President Vladimir Putin's "brutal attack on Ukraine, war has returned to Europe.

"That means that the threat situation has changed," he said. Germany "must be the backbone of deterrence and collective defence in Europe".

In the foreword to the guidelines, Pistorius and head of the armed forces, General Carsten Breuer, said the Bundeswehr needed to refocus on its "core mission" of national defence and "alliance" defence -- referring to the NATO military alliance.

From now on, "all other missions and tasks are subordinate to this," it added.

Following Russia's invasion of Ukraine, Chancellor Olaf Scholz unveiled a special 100-billion-euro ($107 billion) fund to boost the military.

But the challenges are huge, ranging from stocking up quickly enough on new gear, to refitting shabby barracks and finding young Germans willing to sign up.