by the end of this decade."

Russia is verifiably preparing for a conflict with NATO, particularly by strengthening forces in western Russia "at the borders with NATO," the report cites the strategy paper as saying.

As early as next year, Russia could have around 1.5 million soldiers on active duty, according to the paper.

Germany can only counter this threat "with a consistent development of military and society-wide capabilities," the document concludes.

Military personnel and experts developed the strategy paper over the past 18 months to serve as a guideline for the future direction of Germany's Bundeswehr, the Spiegel report said. The defence ministry did not immediately respond to a request for comment. German Chancellor Friedrich Merz recently backed U.S. President Donald Trump's demand to hike NATO's defence spending target to 5% of national GDP, a major shift made possible by a historic loosening of Berlin's constitutional debt brake.