The 62-year-old Antonov is also a longtime diplomat, but he recently completed a nearly six-year stint as a deputy in Russia’s far more hardline defense ministry.

Antonov’s arrival is expected to be a noted shift in Washington’s diplomatic community, where Kislyak was known as an affable fixture on the embassy party circuit, and an experienced political figure with routine official access to U.S. government circles.

“It’s the continuation of a trend we’re seeing throughout Europe, where Moscow is putting in hardline, almost Soviet-style diplomats,” said Heather Conley, who runs the Europe and Eurasia program at the Center for Strategic and International Studies.

After navigating some of the most tense U.S.-Russia relations in recent memory, including Russian President Vladimir Putin’s invasion of Ukraine, Kislyak was rumored to take a post at the United Nations following his near decade of service in Washington. But as the Trump-Russia scandal flared, he was instead recalled to Moscow, though the Kremlin has not said what factored into that decision.

Where Kislyak dealt in soft power — known for lavish parties, calls for better relations between the U.S. and Russia,and a genial if unyielding demeanor — Antonov’s reputation as a hardline Kremlin acolyte precedes him.

As a defense official, Antonov was a key strategist in Moscow’s 2014 invasion of Ukraine, and he received a medal from Putin awarded to officials who participated in the Russia’s annexation of the Ukrainian peninsula. That participation also made him a target of European Union sanctions in 2015, though he was never singled out by U.S. economic penalties.

“He was a very outspoken defender of the whole thing, very nasty in his attacks,” said former U.S. ambassador Alexander Vershbow. “You can expect to hear him talking a lot about NATO encirclement of Russia...he not only says that stuff but he believes it.”

Vershbow, who worked with Antonov on negotiations over ballistic missile cooperation, also said that he is a “much more aggressive public persona” than Kislyak.

He said Antonov’s dedication to Kremlin talking points could be maddening at times. “He wouldn’t let scientific fact get in the way of propaganda,” Vershbow said.

In a March 2015, interview with the Russian network RT, Antonov blamed the U.S. for the then-deteriorating relationship between Washington and Moscow. “They have to change their behavior,” he said of the U.S. “It is not we have started the confrontation between NATO and the Russian Federation.”

A defiant Antonov also told RT that his addition to the EU sanctions list was “very strange and funny and… very stupid.”

Antonov comes to Washington as tensions between the U.S. and Russia reach a fever pitch, in an environment that could be uniquely suited to his aggressive approach. His penchant for taking the hard line is a yet-untested strategy with the Trump administration, which has given clear, early indications that it wants to work more cooperatively with the Kremlin.

Though his reputation precedes him, Antonov is also respected for his skills as a diplomat. And if the Trump administration needs a softer touch, he’s capable of using it.

“I don’t see him as an obstructionist. I don’t think he’s coming here with that kind of mission,” said Matthew Rojansky, a Russia expert who is the director of the Wilson Center’s Kennan Institute. “If he needs to play that role, he will. … He is very smart, and I think very capable of conducting and managing a productive relationship.”

Antonov may find few open doors on Capitol Hill, where suspicion of Russia is at a post-Cold War high. But the political uproar over Trump’s Russia ties weren’t enough to keep his predecessor Kislyak from joining Russian Foreign Minister Sergey Lavrov in the Oval Office in May.

Kislyak, whose farewell dinner was to be hosted by the U.S.-Russia Business Council on Tuesday evening, has fast become one of the most controversial figures in Washington. As investigators probe whether anyone in the Trump camp colluded with the Russian government in swaying the election, Kislyak has emerged as a near-constant presence. His meetings and phone calls with Trump officials, including former national security adviser Michael Flynn and top Trump adviser Jared Kushner, are being heavily scrutinized.

The attention led to speculation that Kislyak was not just a diplomat, but instead was a super-spy, rumors that remain wholly unproven and, according to multiple U.S. officials, unlikely.

Antonov does not appear to have that reputation among diplomatic circles — yet.

“I’m not aware of any particular [nefarious] reputation,” one U.S. official said of him.

Antonov’s Washington to-do list is no small feat. The U.S. and Russia are crossing each other in several high-pressure theaters — Syria, Eastern Europe and Iran, to start. There is continued tension over Russia’s aggressive cyber-strategy, and the ever-lingering questions surrounding its alleged efforts to manipulate the 2016 presidential election.

The State Department did not respond to a request for comment asking why Antonov avoided U.S. scrutiny for his role in the invasion of Ukraine. The Russian embassy did not respond to questions on Antonov’s exact start date.