Zelenskyy talked about his visit one day earlier to the front lines, in the city of Bakhmut in the Donbas region, which has seen months-long fighting, adding that the conflict there during Christmas resembles U.S. troops fighting Nazis at the Battle of the Bulge during World War II.

"Every inch of that land is soaked in blood, roaring guns sound every hour," he said. "The Russians' tactic is primitive. They burn down and destroy everything they see. They sent convicts to the front lines, to the war. They threw everything against, similar to the other tyranny, which is in the Battle of the Bulge."

"Just like the brave American soldiers who held their lines and fought back Hitler's forces during the Christmas of 1944, brave Ukrainian soldiers are doing this same to Putin's forces this Christmas," he said to a standing ovation. "Ukraine holds its lines and will never surrender."

"So here in the front line, the tyranny which has no lack of cruelty against the lives of free people, and your support is crucial -- not just to stand in such fight but to get to the turning point to win on the battlefield," he said.

Zelenskyy said Ukraine's fight is not just to protect their territory from Russia but to preserve their democratic way of life for younger generations.

"The struggle will define in what world our children and grandchildren will live, and then their children and grandchildren. It will define whether it will be a democracy of Ukrainians and for Americans, for all," he said. "This battle cannot be frozen or postponed. It cannot be ignored hoping that the ocean or something else will provide a protection."

"The world is too interconnected and interdependent to allow someone to stand aside," he said. "Our two nations are allies in this battle. And next year will be important, at the point when Ukrainian urge and American resolve must guarantee the future of our common freedom -- the freedom of people who stand for their values."

Lawmakers continued to encourage him with applause.

Zelenskyy opened his speech to a joint meeting of Congress with a direct address to the American people, appealing to shared values of freedom, justice and family in what read out like a letter.

"Dear Americans, in all states, cities and communities -- all those who value freedom and justice, who cherish, as strongly as we Ukrainians, in our cities in each and every family, I hope my words of respect and gratitude resonate in each American heart," he began.

"Dear members of Congress, representatives of both parties who also visited Kyiv, esteemed congressmen and senators from both parties who will visit Ukraine, I am sure in the future," he continued. "Dear journalists, it's a great honor for me to be at the U.S. Congress and speak to you and all Americans."

"Against all odds and doom and gloom scenarios, Ukraine didn't fall," he said. "Ukraine is alive and kicking."

After President Biden's Cabinet walked in, Zelenskyy entered the House chamber to a standing ovation and roaring applause, accompanied by members appointed by House Speaker Nancy Pelosi to escort him.

Zelenskyy, who just one day earlier was visiting soldiers on the front lines of fighting, continued to don his signature army green sweatshirt, green pants and combat boots as he walked up to give his first in-person address outside of Ukraine since Russia's invasion began -- and became the first wartime foreign leader to address Congress since the U.K.'s Winston Churchill during World War II

Zelenskyy stopped to shake lawmakers' hands along the aisle and grabbed hands with Vice President Kamala Harris and Pelosi.

Ahead of Zelenskyy's entrance, Senate Majority Leader Chuck Schumer relayed this message from their closed-door meeting: "He made it clear that without this aid package, the Ukrainians will be in real trouble and could even lose the war."