Russia and Belarus will seek to further grow the threat to Ukraine's northern border in the coming weeks, but a Russian ground invasion from Belarus or Belarusian forces joining the war remains unlikely because of Belarus's own calculations. A surge of military activity in Belarus over the past week is fueling fears in neighboring Ukraine that Russia is preparing to launch a renewed thrust toward Kyiv -- potentially with the help of Belarusian forces. The week began with Belarusian President Alexander Lukashenko's Oct. 10 announcement that he had agreed to deploy a joint contingent of Russian and Belarusian forces in response to alleged threats from Ukraine. On Oct. 14, Lukashenko then announced the introduction of a ''counter-terrorist operation regime'' -- the implications of which are unclear -- and that the deployment of the new Russia-Belarus joint force group, including to his country's southern borders, was connected to an ''elevated terrorist...