The top US military officer told lawmakers Tuesday that the world is becoming more unstable and the “potential for significant international conflict is increasing, not decreasing.” Chairman of the Joint Chiefs Gen. Mark Milley and Defense Secretary Lloyd Austin appeared before the House Armed Services Committee in their first testimony before Congress since Russia’s invasion of Ukraine.

The two Pentagon leaders said the threats from both Russia and China remain significant, while they defended the US approach to the war and the flow of arms the US is sending to Ukraine. Milley said that Russia’s invasion of Ukraine is “the greatest threat to peace and security of Europe and perhaps the world” in his 42 years serving in the US military, but added it was “heartening” to see the world rally around Ukraine.

“The Russian invasion of Ukraine is threatening to undermine not only European peace and stability but global peace and stability that my parents and a generation of Americans fought so hard to defend,” Milley said.

Milley was asked about the need to reallocate forces to Europe’s eastern flank, where NATO allies are worried that they may be Russia’s next target. “My advice would be to create permanent bases but don’t permanently station (forces), so you get the effect of permanence by rotational forces cycling through permanent bases,” he said.

“I believe that a lot of our European allies, especially those such as the Baltics or Poland and Romania, and elsewhere — they’re very, very willing to establish permanent bases. They’ll build them, they’ll pay for them.” Austin added that he recently visited and spoke with leaders in the Baltics, noting that they made it clear they value U.S. troops there.

“We’ll continue to work with NATO to assess what the requirements will be moving forward,” Austin said. “We will be part of that solution.” The Pentagon is continuing to review its troop numbers across Europe, and whether to add more or shift some of those already there to other locations. Milley said Tuesday that while there are no decisions yet, there’s a possibility, if not a probability” of increase U.S. troops in Europe, and that need could be filled by rotational forces.