Recently, I wrote from Mariupol, Ukraine, that it would be a mistake for Russian President Vladimir Putin to attack this once Russia-friendly city. The United States may soon commit a similar error, if it makes a show of arming Ukraine.

Some very smart and informed people, from Zbigniew Brzezinski to Steven Pifer, have argued cogently for doing so. Now US President Barack Obama’s pick for the No 2 spot in the State Department, Antony Blinken, has said he, too, is open to the idea.

Ukraine certainly needs the weapons, especially around Mariupol. The city feels oddly unfazed, given that it’s in the crosshairs of a promised new rebel offensive, and that the only reason the last one — in late August — failed was thanks to a timely cease-fire. Back then, however, Mariupol was defended by just a lightly-armed volunteer militia, the Azov Battalion. Now, says Mayor Yuriy Khotlubey, the city has three lines of defence, heavy artillery and a substantial force of regular army and national guard that’s been digging in around the city.

The Azov Battalion, with their disturbing swastika-like insignia, has been relegated to patrolling the city from a shabby base near one of the city’s huge steel plants. The military’s new insignia for the uniforms of all Mariupol defence forces says “Only Victory”.

This popular faith in Mariupol’s defences is touching, but misplaced. The last Ukrainian emplacement facing east is just past the edge of the city. The rebels are about 16 km (10 miles)away and the Russian border, 20 miles further. Whether now or in the spring, Russia can deploy whatever it takes to open a land corridor through or around Mariupol to Crimea.

In the meantime, a front line has developed roughly along the Kalmius River that runs northeast from the city. Separatist fighters, often equipped with drones for spotting, test the Ukrainian defences daily. Villages are getting hit by inaccurate shelling from both sides, and in many cases are being cut off from power, heat and safe access to supplies. Their situation is desperate.

The war is also increasingly dirty. On November 2, a car bomb struck the main checkpoint at the eastern end of Mariupol, killing two. The driver, who briefly survived, said the bomb was detonated remotely by a drone. Almost 1,000 people have been killed since the September 5 ceasefire, according to a United Nations report, and in rebel-held areas, law and order have collapsed. Such chaos can keep Ukraine destabilised for years until it buckles — which is probably the intention.

To stabilise things and deter any rebel offensive, Ukraine’s military would need significant quantities of sophisticated defensive weapons, such as guided anti-tank and anti-aircraft systems. If these were US-made, then trainers would be needed, too, to teach Ukrainian soldiers how to use them.

Most people in Mariupol seem to want this, including the mayor. One 25-year old native Russian speaker from the Azov Battalion (he’s from “occupied” Lugansk and didn’t want give his name) was even more adamant. “We can’t do anything against their artillery with these,” he said, shaking his Kalashnikov. Even assuming that Russia isn’t looking for compromise and will push forward until Ukraine collapses, though, US arms for Ukraine are a bad idea.

Why? Most important, they would make real the myth that Russia is responding to Nato aggression in Ukraine. Nothing is more likely to raise support in Russia for going to war in Ukraine — at the moment, it’s just 13 per cent — than footage of US weapons killing Russians on the border.

Second, there are few angels in this war. A Human Rights Watch report has convincingly tied Ukrainian forces to the use of cluster bombs in residential areas — a war crime according to most countries. (Regrettably, Ukraine, Russia and the US have not signed the Convention on Cluster Munitions.) Ukraine will try to crush the rebels, at great human cost, if it believes, however mistakenly, it has the means and the US at its back.

Finally, US weapons are sub-optimal for Ukraine. What’s needed are the kind of Soviet-designed arms that Ukrainian troops already know how to use, and that can’t play the role of smoking guns for Russian propagandists.

In August, Croatia considered selling Ukraine 14 Soviet-era MI-8 helicopters, recently upgraded. (In the three-way deal that was on the table, Croatia would have gotten last-generation, but Nato compatible, US Blackhawks.) Such resupply arrangements are the best approach. The arms given to Ukraine in such deals should be defensive deterrents — in particular, guided anti- tank and anti-aircraft weapons. The US could step in with purchase money, replacements for Nato allies and non-lethal gear such as night-vision goggles, needed to reduce the toll from sniper fire after dark.

If the US starts arming Ukraine directly, however, then, in the words of Galina Odnorog, who since April has been leading the local effort to equip Ukrainian forces, “This won’t just be a local conflict any more, it will be World War III.” If not world war, a cycle of military escalation almost certainly would follow any major injection of lethal US weaponry into eastern Ukraine. It may be distasteful to reply to Putin’s “hybrid” war with similar subterfuge, but it’s all that makes sense.

— Washington Post

Marc Champion writes editorials on international affairs for Bloomberg View.