Since the end of the Cold War, a variety of leaked diplomatic cables, captured operatives and acts of espionage, like this summer’s hack of the Democratic National Committee, have served as reminders that Russia and the United States continue to routinely spy on each other.
On Thursday, the United States said it would expel 35 officials in retaliation for what American spy agencies said was Russian interference in the presidential election. It was the largest number of diplomats forced to leave the United States since 2001, when 50 officials were sent back to Russia after the arrest of Robert Philip Hanssen, a veteran F.B.I. agent who was caught spying.
The United States expelled two Russian diplomats in retaliation for a bizarre episode outside the United States Embassy in Moscow, in which a Russian police officer attacked an American diplomat.
Russian television broadcast a short clip of the scuffle and said the American was an undercover Central Intelligence Agency operative who had refused to show identification before entering the embassy. The State Department said the American was an “accredited diplomat” who had been assaulted as part of systematic harassment of American embassy staff by the Russian authorities.
In May 2013, the Russian government ordered an American Embassy official, identified as Ryan C. Fogle, to leave the country. His expulsion followed an almost comical arrest in which he was caught carrying two wigs — one blond and one brown — a Moscow street atlas, $130,000 in cash and a letter offering “up to $1 million a year for long-term cooperation.”
In 2010, 10 Russians accused of being members of a sleeper cell were deported after pleading guilty to conspiracy in a federal court in Manhattan. As part of a deal, the spies were swapped for four Russian prisoners, three of whom were serving sentences on treason convictions.
The case, which was often compared to the plot of a spy novel, included evidence of letters written in invisible ink, buried cash and a red-haired beauty whose romantic exploits and risqué photographs made for tabloid fodder.
In March 2001, the United States expelled 50 Russian diplomats in the wake of the arrest of Mr. Hanssen, who was a counterintelligence expert at the F.B.I. and had spied for Moscow for more than 15 years.
American officials said Mr. Hanssen had been paid hundreds of thousands of dollars after he volunteered to turn over United States secrets to Russia, and they blamed the Kremlin for not turning him down or turning him in. In response, Russian officials kicked out several American diplomats.
In February 1994, shortly after the arrest of Aldrich H. Ames, a career C.I.A. officer who turned out to be a double agent, United States officials expelled a senior Russian diplomat, Aleksandr Lyskenko, whom they called a top officer of the Russian Foreign Intelligence Service. According to the State Department, Mr. Lyskenko was “in a position to be responsible” for Mr. Ames’s activities as a very productive mole.
Although Mr. Ames’s treachery was almost certainly the most damaging breach of American intelligence since World War II — Moscow executed several operatives whom he had betrayed — Washington’s response was considerably less severe than it would have been in Soviet times, or now. In the years after the fall of the Soviet Union, the Clinton administration, eager to encourage friendly relations and reform, supported the new government of President Boris N. Yeltsin. Before Mr. Lyskenko was told to leave the country, the Americans even gave the Russians the option of voluntarily sending him back home.
Fifty-five Soviet diplomats were expelled by President Ronald Reagan in November 1986 in an effort to curb espionage activities. Similarly, the authorities in Moscow ordered 260 Soviet employees of the United States Embassy in Moscow to stop working.
It was the largest number of diplomatic officials to be expelled by the United States at once. The conflict arose after a Soviet employee of the United Nations, Gennadi F. Zakharov, was arrested on espionage charges. The Russians responded by arresting Nicholas S. Daniloff, the Moscow correspondent for U.S. News & World Report, and accusing him of spying. Mr. Daniloff was released two weeks later.