St. Louis Post-dispatch on red lines:

Ukrainian President Volodymyr Zelenskyy appealed directly to Congress Wednesday to establish a no-fly zone over his country — a request that the Biden administration has already rejected. He wants Poland’s MIG-29 jets so Ukraine can fight for control of Ukrainian skies instead of opening them so Russian planes can attack civilian areas at will. Again, the Biden administration says no.

In the public relations war that is crucial to galvanizing Western solidarity behind Ukraine, Zelenskyy has a winning message of stalwart resistance against superior Russian forces. Russian President Vladimir Putin is winning his own twisted public relations campaign by communicating an effective visual message that anyone who dares stand in his way will be crushed mercilessly.

Against that backdrop, the Biden administration’s message comes off as nervous hand-wringing. Avoid offending Russia at all costs, but boy, we’ll sure show ’em with sanctions.

This is not to suggest the United States is merely watching helplessly from the sidelines. Billions of dollars in U.S. military and humanitarian aid are pouring into Ukraine, including anti-tank rockets and Stinger shoulder-fired anti-aircraft missiles. That aid has been overt, which creates confusion in the public’s eyes when Biden insists that transferring Nato-member Poland’s Mig-29s to Ukraine would risk provoking a superpower confrontation. Yet NATO weaponry can already be seen on videos destroying Russian tank convoys and shooting down aircraft.

The logic doesn’t quite square that it’s OK for the West to supply some lethal weaponry that downs Russian planes and destroys its tanks, while it’s not OK for other weaponry that would accomplish the same goal.

Some useful background: In late 2013, at the height of the Syrian civil war, then-president Barack Obama painted himself into a corner by warning Syria it would cross a red line if it used chemical weapons. Russian-backed Syria then used chemical weapons, and Obama backed away from his threat to respond militarily.

U.S. resolve was tested, and the United States backed down. Less than four months later, Putin moved his forces into Ukraine’s Crimean Peninsula and seized it. Then he deployed forces to support separatist militias in eastern Ukraine. Red lines crossed again, with no serious U.S. response.

The Biden administration smartly seems determined not to repeat Obama’s mistake by setting red lines it isn’t prepared to enforce. A no-fly zone would establish one such red line, and Sen. Roy Blunt, R-MO., on Wednesday echoed the administration’s position that America dare not go that far.

But U.S. avoidance won’t erase other red lines. Russia could use chemical weapons in Ukraine or even tactical nuclear devices. It could move against NON-NATO neighboring states like Moldova, or weaker NATO states like Lithuania — all just to see how far Putin can push Biden. From the administration’s response so far, Putin would be correct in assuming that even the sky’s not the limit.