Ukraine had been waiting for this green light for months. In a visit to Kyiv on Wednesday, May 15, US Secretary of State Antony Blinken hinted that Ukrainian forces could strike Russian territory with weapons supplied by the US, for the first time since the Russian invasion in 2022. "We have not encouraged or enabled strikes outside of Ukraine, but ultimately Ukraine has to make decisions for itself about how it's going to conduct this war," said Blinken, opening up the possibility of Western military materiel being used against Russian units located beyond Ukraine's borders.

Since the start of the conflict, Ukraine's allies had been adamant that their missiles, drones or bombs could not be used to bomb targets outside of Ukraine's own territory. Only Ukrainian soil − including Russian-occupied Crimea and Donbas regions − could be targeted. This restriction, imposed out of concerns over a potential escalation with Moscow, has been heeded by Kyiv, which has been too dependent on Western arms deliveries to break any rules made by its allies.

Moscow's May 10 offensive in the Kharkiv region has changed all that. For weeks, Ukrainian intelligence services had been warning that Russian troops were massing along the country's northeastern border, and explaining that Kyiv's forces lacked the means needed to strike them using solely the country's home-made arsenal: The explosive charges carried by Ukraine's drones are too weak to "deal with" large numbers of soldiers, unlike the cluster munitions supplied by the US. The Ukrainians also lacked the quantity of artillery shells needed to carry out saturation attacks, designed to destroy massed men and equipment.

"US policy has effectively created a vast sanctuary in which Russia has been able to amass its ground invasion force and from which it is launching glide bombs and other long-range strike systems in support of its renewed invasion," writes Georges Barros, a researcher at the American think tank Institute for the Study of War, in a report published on May 13. According to Ukrainian officials, 30,000 Russian troops have crossed the border into the Kharkiv region, with another 50,000 being held in reserve to support them.

As a sign that this pivot in the Western posture had been carefully considered, the American shift was preceded by an initial British policy inflection. During a visit to Kyiv on May 3, Foreign Secretary David Cameron said he was ready to authorize Ukrainian strikes on Russian soil with weapons supplied by London. "Just as Russia is striking inside Ukraine, you can quite understand why Ukraine feels the need to make sure it's defending itself," the former prime minister said.

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