Yet another cease-fire agreement on Ukraine has been signed in Minsk. It went into effect Sunday amid low expectations of success.

This is the second such agreement to come out of Minsk. The previous deal was signed in September. It collapsed almost immediately. There is precious little confidence that Minsk II will pan out any better. The best that German Chancellor Angela Merkel, who helped negotiate the deal, could say was that it offered a “glimmer of hope.”

The timing of the agreement was no accident. The fighting was getting more intense because the Russians were escalating the conflict. In response, Washington and Brussels started talking about the need for more sanctions against Moscow. This set off alarm bells in Berlin and Paris.

When American legislators proposed arming the Ukrainians, Mrs. Merkel and French President Francois Hollande, who oppose this, swung into action. They began negotiations with the Russians without direct U.S. involvement. The hope appears to have been to nip the arms proposal in the bud with a cease-fire agreement.

European queasiness over arming the Ukrainians may be understandable. After all, they argue, it’s their neighborhood and a war with Russia would hit them directly. But they need to consider that not arming the Ukrainians may make war more likely, not less.

First of all, we are talking about defensive, not offensive weapons. The military package being discussed involves anti-tank/armor weapons that would be effective against the Russian T-72 tanks used by the Kremlin-backed separatists in Ukraine. Also contemplated is counterbattery radar that could help the Ukrainian forces locate the origins of artillery strikes. Other materials could include secure communication equipment and unmanned aerial vehicles that would improve the situational awareness of the Ukrainian forces on the battlefield.

Without these weapons and equipment, the Ukrainians could very well lose control over all of eastern Ukraine. From there, the Russians could establish a sanctuary base from which to destabilize the rest of the country. The Russians want to force the Americans and the Europeans to accept their presence inside Ukraine as a hard and permanent fact. Nothing would make this easier than the defeat of Ukrainian forces.

Mr. Putin is likely to press his military offensive against Ukraine until he meets a cost higher than he is willing to pay. Right now, he has an open road to do whatever he wants because that toll is very low. It could be different if he sees that the “frozen conflict” he longs for won’t be the cake walk he expects. Right now, the casualties and costs are too low to deter him from further escalation. A higher cost could force him to think otherwise.

To be sure, if we supplied the Ukrainians with defensive arms, Mr. Putin would throw a temper tantrum. He would also escalate the conflict in the short term to scare the already terrified Europeans into thinking he is about ready to start World War III.

That would be a bluff. In fact, Mr. Putin enjoys escalation dominance in the Ukraine conflict because he senses the West is afraid of him. That psychology needs to be reversed. Mr. Putin wants Ukraine as cheaply as he can get it, and lowering the price for him is an inducement, not a deterrent, to further escalation.

We’ve already started helping Ukraine militarily, and the sky has not fallen. The U.S. is sending 600 paratroopers to Ukraine to train their troops, and World War III hasn’t broken out. If and when Minsk II collapses, we should step up what we’ve already begun. We need to start helping the Ukrainians defend themselves.

 - Kim R. Holmes is a distinguished fellow at The Heritage Foundation.