Retired Adm. William McRaven argued, during a recent discussion of the challenges the new Biden administration faces, that Russian President Vladimir Putin has outplayed the U.S. and Russia is the greatest external security threat.

“I am often asked where do I think the greatest external security threat is, and I always point to Russia,” McRaven, a former Navy SEAL and special operations commander, said at a Chatham House event on Tuesday. “A lot of people think about China, but Russia jumps to mind first.”

While he acknowledged that Russia is not the superpower it once was, he stressed that “Putin has outplayed us.”

“He has played the great game better than anyone on the world stage,” McRaven said of the Russian president. Pointing to Russian actions in Crimea, Ukraine, Syria, and even the U.S. that were detrimental to American interests, he said: “Putin is a very dangerous person.”

China is often regarded as the pacing threat for the U.S., and during the Trump administration, tremendous emphasis was put on countering China with less attention paid to Russia.

Nonetheless, Russia is a great power rival, listed as a leading threat alongside China in the 2018 National Defense Strategy.

“We do need to find areas where we can partner with the Russians,” McRaven said, “but make no mistake about it, I think we need to take a hard line with respect to Russia… We need to let Putin know that there are lines you just shouldn’t cross.”

McRaven praised President Joe Biden’s first phone call with Putin, where the president, according to a White House readout, “made clear that the United States will act firmly in defense of its national interests in response to actions by Russia that harm us or our allies.”

Biden is said to have discussed arms control concerns, asserted U.S. support for Ukraine, and pressed Putin on the massive SolarWinds cyberattack that affected a number of federal government agencies and bureaus. He also discussed election interference and the poisoning of Kremlin critic Alexei Navalny.

“I was pleased to see [that] the president in his first phone call with President Putin addressed Alexei Navalny issue,” McRaven said. “I don’t think President Trump would have done that.”

As president, Donald Trump did not condemn Russia over the poisoning of Navalny, who Russia recently put in prison.

Commenting on his discussion with Putin, Biden said Thursday that he “made it clear to President Putin, in a manner very different from my predecessor, that the days of the United States rolling over in the face of Russia’s aggressive actions — interfering with our election, cyber-attacks, poisoning its citizens — are over.”

“We will not hesitate to raise the cost on Russia and defend our vital interests and our people,” he added.

McRaven argued Tuesday that the U.S. needs to not only make its position clear to Russia, but it also needs to rebuild and leverage alliances “to make sure that Russia understands how they need to play.”

The Biden administration has made rebuilding alliances, reengaging in international affairs, and leading with confidence and humility its priorities. The president’s foreign policy approach stands in stark contrast with Trump’s “America First” policies.

During his presidency, Trump was criticized by Democrats and some Republicans for pushing away allies and partners while at times cozying up to adversaries.

In particular, critics expressed concern as Trump struck a conciliatory tone towards Russia, despite warnings from across the intelligence community and other parts of the U.S. government that Russia was engaged in activities that harmed U.S. interests.

McRaven, who voted for Biden despite considering himself a conservative, was an outspoken critic of Trump’s policies.

In an opinion column published in August, McRaven wrote that Trump was “actively working to undermine every major institution in this country” as the U.S. struggled with “rising threats from China and Russia,” among other challenges.

One of his more famous op-eds was a 2019 article titled Our Republic Is Under Attack From the President, in which he said: “If this president doesn’t demonstrate the leadership that America needs, both domestically and abroad, then it is time for a new person in the Oval Office.”

He said that Trump’s actions threatened the trust of American’s allies and partners.

“If our promises are meaningless, how will our allies ever trust us? If we can’t have faith in our nation’s principles, why would the men and women of this nation join the military,” McRaven wrote. “And if they don’t join, who will protect us? If we are not the champions of the good and the right, then who will follow us? And if no one follows us — where will the world end up?”

McRaven served nearly four decades in the military. As commander of Joint Special Operations Command, he oversaw Operation Neptune Spear, the successful military raid that killed the al Qaeda leader Osama bin Laden in 2011.

After retiring from the Navy in 2014, he went into academia and has written best-selling books on leadership, including Make Your Bed: Little Things That Can Change Your Life … and Maybe the World and Sea Stories: My Life in Special Operations.