Commentary President Joe Biden, the weakest president in modern American history, having presided over the treacherous and bloody collapse of Afghanistan, has now made an open-ended pledge to Ukraine’s leader, Volodymyr Zelensky, that the United States would “respond decisively” should Moscow invade Ukraine. Biden’s pledge appears to have been made without coordination with America’s NATO allies, and NATO itself has not discussed the issue. Ukraine is not a NATO member and therefore no NATO country, including the United States, has a treaty obligation to defend it. On the other hand, NATO Secretary General Jens Stoltenberg said in a December message to Zelensky that “NATO stands with Ukraine. All Allies support Ukraine’s sovereignty and territorial integrity.” And like Biden’s pledge, Stoltenberg’s declaration was not approved by NATO’s members. American and NATO-directed saber rattling threatens European peace more than it threatens Russia. Europe is in no condition to foster a conflict with Russia that could lead …