Defense Secretary Lloyd Austin said Ukraine’s courage in the face of invading Russians is a historic showing of resistance.

Secretary of Defense Lloyd Austin has praised the Ukrainian military for responding to the Russian invasion in a way that he says “will go down in military history.”

Austin stressed alleged atrocities by Russian forces in Ukraine while tweeting praise for the defensive effort on Friday. Despite heavy losses mounting on both sides, Ukrainian forces have managed to fend off the much larger Russian Army for more than two months, despite many experts predicting a swift defeat at the beginning of the war.

“Ukraine’s hospitals have been bombed,” Austin tweeted. “Their citizens have been executed. Their children have been traumatized. And yet, despite all that, they have done a magnificent job defending their sovereignty. Ukraine’s valor and skill will go down in military history.”

Austin’s tweet echoed remarks that he made earlier this week during a speech at Germany’s Ramstein U.S. Air Base, where he met with military leaders from more than 40 countries as part of the new Ukraine Defense Consultative Group.

Austin added in Germany on Tuesday, “You know, the Battle of Iwo Jima took 36 days,” he continued. “The Battle of the Bulge lasted 40 days. And Ukraine has now beaten back the Russian military for 62 days.”

Austin added that Ukrainian resistance had “brought inspiration to the free world,” while the U.S. and other countries had provided assistance that Russian President Vladimir Putin “never imagined” would happen “so swiftly and surely.”

The defense of Ukraine has exceeded the expectations of many. Just before the invasion began, three U.S. officials told Newsweek that they expected Kyiv to fall “within days” and that Ukrainian leadership would crumble about a week later.

An end to the war is not currently in sight, with peace negotiations between the warring countries having stalled after Russia shifted its focus to a large-scale attack in Ukraine’s eastern Donbas region.

During a joint press conference with Austin in Poland this week, U.S. Secretary of State Antony Blinken said that Russia had “already failed” in achieving its goals while “Ukraine is succeeding” and could win the war.

On Friday, NATO Deputy Secretary-General Mircea Geoană predicted that the war could stretch on for many more months or years during an interview with the BBC.

“It’s clear that the next few days and weeks could prove decisive, but the war would probably take longer,” Geoană said. “Could be weeks, could be months, could be even years—it depends on a lot of factors.”

“But, in the end, probably this will be fought and won, hopefully, by Ukraine on the battlefield,” he added.