"Russia is preparing for a war with the West," Bruno Kahl, the head of Germany's foreign intelligence service, said in late November. But it's not likely to be a large-scale attack into NATO territory, the intelligence chief warned. Moscow could opt for a limited incursion or upping its hybrid warfare tactics to probe the alliance's conviction, Kahl said. NATO is trying to prepare for both scenarios: an all-out war, and less obvious techniques designed to undermine stability in the alliance's member countries. "There are multiple options for Russia to test the cohesion of the alliance," including limited land grabs, the...