The strike on the Internet Research Agency in St. Petersburg, a company underwritten by an oligarch close to President Vladi­mir Putin, was part of the first offensive cyber campaign against Russia designed to thwart attempts to interfere with a U.S. election, the officials said.

“They basically took the IRA offline,” according to one individual familiar with the matter who, like others, spoke on the condition of anonymity to discuss classified information. “They shut ‘em down.”

The operation marked the first muscle-flexing by U.S. Cyber Command, with intelligence from the National Security Agency, under new authorities it was granted by President Trump and Congress last year to bolster offensive capabilities.

Whether the impact of the St. Petersburg action will be long-lasting remains to be seen.