The May 30 drone attack on Moscow, with at least three unmanned aerial vehicles hitting apartment blocks, is the most dramatic evidence so far of a major shift in the Russo-Ukrainian war: The fighting is now taking place in Russia’s own territory as well as in Ukraine.

The Ukrainian government retains a fig leaf of deniability, as Ukraine’s Western allies officially frown on offensive action on Russia proper, as opposed to on Russian-occupied Ukrainian regions. So Kyiv has not claimed responsibility for the latest drone attack, for previous attempted drone strikes on the Kremlin and on the Krasnodar region in the south of Russia or for the recent incursion of a small group of fighters using Western military vehicles into Russia’s southern Belgorod region. Nor has it admitted shelling villages and towns or derailing trains on the Russian side of the border. Too many of these incidents have happened, however, to see them as anything other than a Ukrainian tactic of taking the war to the Russians.

The tactic is a gamble with a transparent short-term military upside and a potential long-term psychological downside, which Ukraine has managed to avoid so far by keeping the civilian casualties low.