The news that the U. S. Pentagon and State Department have drawn up plans to supply Ukraine with anti-tank missiles and other defensive weapons has provoked a flurry of opinion pieces for and against the move.

The arguments fall into two broad camps: those arguing for arming Ukraine say such weapons will deter further aggression from Russia, while those arguing against say that arming Ukraine will only anger the Kremlin and provoke it to escalate the conflict, or encourage Ukraine to go on the offensive itself.

Which argument is valid?

The keys to resolving this question are the prefix “anti-” and the adjective “defensive.” U.S. officials are not proposing to provide Ukraine with swords, but with shields.

Those arguing against arming Ukraine must ask themselves why the Kremlin would escalate the fighting against a better-defended Ukraine, when its previous offensives against a weaker Ukraine, notably at Avdiyivka this winter and at Maryinka in June 2015, have failed.

The argument that arming Ukraine could embolden Kyiv to attempt its own offensive is likewise illogical. For this, Ukraine would require large amounts of armor and, more significantly, enough air power to establish air superiority over large portions of the eastern territory occupied by Russia. Ukraine, for now, simply does not have this capability, and U.S. officials are not proposing to give it to them.

By far the most likely scenario for a further escalation of the war would be an advance by Russia’s proxy forces: their leadership have many times expressed their desire to take more territory; their tanks are often daubed with the words “Na Kiev” in Cyrillic, or “To Kyiv.”

The proxy forces’ aggressive plans could be foiled, and their tanks stopped in their tracks, if Ukraine had access to superior defensive weapons such as the U.S.-made Javelin anti-tank missile. The Javelin, which has a range of more than two-and-a-half miles and which plunges onto its target from above to break through a tank’s weaker top armor, would be more than a match for the tanks of Russia’s proxy forces — most of which are old T‑64s from Russia’s reserves.

The case is clear, and it has been since the beginning of Russia’s war on Ukraine. Russian dictator Vladimir Putin will not stop until the costs of war become too high. Giving Ukraine defensive weapons would make it too costly for Putin to attack further. Arm Ukraine.