The Kremlin is "specifically aligning both its industry and leadership structures with the requirements of a large-scale conflict against NATO by the end of this decade," the news magazine wrote on Friday, quoting from the paper.
Russia has strengthened forces in particular along NATO borders in western Russia and could have around 1.5 million soldiers on active duty by 2026, Spiegel reported, citing the paper.
The report warns that Germany can only counter the threat by consistently developing its military and societal capabilities.
The strategy paper was developed by military personnel and experts as a guideline for the future direction of Germnay's military, Spiegel said.
In May, German Chancellor Friedrich Merz surprised NATO allies by signalling plans to massively boost defence spending to five percent of GDP as demanded by US President Donald Trump.
The spending hike is possible as Merz's coalition government secured major financial firepower – an easing of debt rules and approval for hundreds of billions in extra funding for defence and infrastructure.
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