ALMOST three months have passed since Russia annexed Crimea and began stirring up rebellion in eastern Ukraine. For most of that period the hope of Western leaders has been that tensions there will gradually dissipate and that the crisis will just go away. That hope now looks deluded.

The argument was that Vladimir Putin, Russia’s president, had got most of what he wanted in Crimea and eastern Ukraine, not least a big boost in popularity at home. Partly thanks to two rounds of sanctions against individuals close to him, he had blinked: hence his decision to pull troops back from the border and more or less to accept Petro Poroshenko as Ukraine’s legitimate president after his election on May 25th. Thus there is no need for further sanctions that could wreak damage on Europe’s shaky economies as well as on Russia.

Violence begets violence

The past two weeks have exposed this as wishful thinking. Violence has increased in eastern Ukraine as the government in Kiev has sought to regain control and the rebels have fought back. The government’s unilateral ceasefire announced this week looks unlikely to work (see article). Evidence of deeper Russian involvement is ever clearer: not just rising numbers of Chechen and other Russian mercenaries but also the supply of weapons, including missiles that may have been used to shoot down a Ukrainian military aircraft, and even tanks that have rumbled over the border. Meanwhile hopes that Mr Poroshenko might strike a deal on gas supplies from Russia have been thwarted because, for the third time in eight years, the Russian gas giant, Gazprom, has turned off the taps. That may affect the European Union because Russia accounts for a third of the EU’s gas imports, and half of them flow through Ukraine.

Not to respond to renewed Russian meddling would be dangerous and wrong. If the rebels start losing ground, the Russians may step up their support. Mr Poroshenko still plans to sign the trade deal with the EU that was spurned by his predecessor, Viktor Yanukovych, last November, triggering the Maidan protests in Kiev that led to Mr Yanukovych’s departure. Ukraine’s government needs further support. The EU should accelerate efforts to become less reliant on Russian energy. That implies guarding against a gas cut-off by completing interconnectors that allow supply from the west as well as the east, searching for new gas sources and building more terminals for liquefied natural gas. It also means that the EU must pursue vigorously its antitrust case against Gazprom, which operates as a monopolistic arm of the Russian state, not a normal firm.

A third round of sanctions is also needed. The goal of the first two rounds was to persuade Mr Putin to stop meddling in eastern Ukraine. So far he seems to have shelved thoughts of full-scale invasion, but he is intervening more than ever. Appeasers fret that fresh sanctions could provoke more Russian hostility. Yet, as NATO’s deputy secretary-general has noted, Russia has already chosen to treat NATO as an adversary, one reason why countries such as Sweden and Finland are considering joining (see Charlemagne). There is much scope for further Russian revanchism in places like Moldova or Georgia.

Experience shows that the only way to deter bullying is to stand up to it, even if that comes at a price. Having threatened a third round of sanctions, the West should make good on its threats—unless and until Mr Putin stops nakedly interfering in eastern Ukraine. Anything else would be an invitation.