Want smart analysis of the most important news in your inbox every weekday along with other global reads, interesting ideas and opinions to know? Sign up for the Today's WorldView newsletter.

On Wednesday, Britain issued its official retaliation to the attempted poisoning of an ex-Soviet spy on its soil: Prime Minister Theresa May ordered 23 Russian diplomats — deemed “undeclared intelligence officers” — expelled from the country, a move that immediately drew comparisons to the Cold War.

Britain believes that Russia is behind the use of a Russian nerve agent in the cathedral city of Salisbury as part of an attempt to assassinate Sergei Skripal and his daughter, Yulia. The attack left the pair comatose and in critical condition, while forcing 18 others to receive medical treatment.

“May repeated the conclusion of British investigators that Russia had either deployed or lost control of a dangerous nerve agent used in the attack — targeting the former spy and his daughter — and said Russia’s defiant response has 'demonstrated complete disdain for the gravity of these events,' " my colleagues in London reported. In addition to the expulsions, the largest of their kind in Britain since 1985, Britain is imposing a host of other relatively minor penalties.

Moscow, which has a track record of striking at targets living in Britain, denied any involvement in the episode, and senior Russian officials ignored an ultimatum for an explanation of the incident. Meanwhile, its media outlets and diplomatic corps voiced outrage — and plenty of ridicule.

As a range of Kremlin mouthpieces decried mounting Russophobia in the West and the Russian Embassy in London described the new punitive measures as "totally unacceptable, unjustified and shortsighted," the Russian Foreign Ministry mocked Britain's finger-pointing.

On Russian television, a man wanted in the 2006 poisoning of a former KGB agent living in Britain was casually brought on as a guest to discuss this week's news.

The Russians, May lamented to Parliament, “have treated the use of a military-grade nerve agent in Europe with sarcasm, contempt and defiance.”

There are clear reasons why the Russians seem to be taking the situation lightly. Russian President Vladimir Putin is on the campaign trail less than a week from an almost-certain reelection, and would hardly want to strike a conciliatory tone against the foreign governments he loves to challenge. His politics are built on a defiant nationalism, drawing on both a desire to revive Russia's lost imperial glory as well as lingering resentment of the West.

“The trouble is that Russia probably doesn’t much worry about diplomatic expulsions, and British sanctions would add little to the broad range of Western sanctions already in place over the annexation of Crimea,” a New York Times editorial noted this week. “Yet if Russia’s message is that no 'traitor' is safe anywhere, it should be in the interest of every nation to send an indelible message to Mr. Putin that he cannot deploy his weapons of war anywhere he wants.”

On Wednesday, a session of the United Nations Security Council offered tough rhetoric on Russia but little meaningful action. There's no consensus within the European Union over new potential sanctions on Russia, and the tortured negotiations over Brexit has fundamentally impaired May's ability to coordinate collective action.

“The episode underlines the extent to which UK’s post-Brexit foreign and security relations with the EU remain unresolved,” wrote Patrick Wintour, the Guardian's diplomatic editor. “Britain as a third party would not be automatically consulted on common foreign and security policy, including further sanctions coordination, but both sides have been deferring talks until the outline of a trade deal becomes clearer.”

Further complicating the situation is the sheer weight of the Russian presence in Britain. For more than a decade, London has seen the ceaseless arrival of wealthy Russian emigres, including oligarchs fleeing the Kremlin and those still in Putin's good graces. With what some critics claim are looted assets, they have reshaped the British capital's real estate market and social scene — and led to a proliferation of spooks.

“Russia now has more intelligence agents deployed in London than at the height of the Cold War,” Ellen Barry of the New York Times reported. “They serve a variety of functions, including building contacts among British politicians. But the most important task is to keep an eye on the hundreds of heavyweight Russians — those aligned with President Vladimir V. Putin, and those arrayed against him — who have built lives in Britain, attracted by its property market and banking system.”

It’s unclear whether May will consider any further action on pro-Putin oligarchs living within Britain, but she said that she believed the country’s money-laundering laws were strong enough to deal with “corrupt elites.” Some prominent Russian journalists saw that as mere avoidance.

Putin’s most vocal opponent, anti-corruption activist Alexei Navalny, also expressed his concerns about the thrust of the Western response. “One scenario, as it seems to me, is Putin's comfortable scenario,” he told ABC News this week, gesturing at symbolic sanctions and the sort of expulsions ordered Wednesday.

“There is a second option,” he said, “that would really be painful for Putin and his corrupt circle that consists of applying targeted sanctions on those oligarchs and state officials whose families have been based for a very long time in Great Britain.” Those do not seem to be in the cards yet.

Meanwhile, even as his lieutenants criticized Moscow, President Trump was slow to denounce what could be a state-sponsored Russian attack on the soil of one of his nation's closest allies. The administration waited until Wednesday evening to blame Russia for the attack. Trump often leaps to conclusions about Islamist terrorist attacks before all the facts are known. His relative caution in this case is conspicuous to European observers — and another indication of a larger, more troubling rift.

“Trump’s mixture of hostility and indifference to the European project, its trading power and its liberal, democratic values, is hardly news,” wrote Natalie Nougayrède, the former editor of French daily Le Monde. “But with the early signs of a trade war, and the growing evidence of the president’s disdain for Britain’s predicament just when transatlantic empathy was expected, we see his estrangement from historical norms in sharp focus.”

Want smart analysis of the most important news in your inbox every weekday along with other global reads, interesting ideas and opinions to know? Sign up for the Today's WorldView newsletter.