The Ukrainian leader sought to convey the reality of the war to Washington.

In his dramatic, daylong visit to Washington, President Volodymyr Zelensky of Ukraine sought to bring the sounds and smells of the war’s front lines to the decision makers in White House and the Congress, who he said had the ability to speed up Ukraine’s victory and bring the war to an end.

“Every inch of that land is soaked in blood; roaring guns sound every hour,” he said of Bakhmut in the country’s east, where his army is holding ground in one of the bloodiest campaigns of the war. “The Russians’ tactic is primitive. They burn down and destroy everything they see.”

While support for Ukraine has broad support in Congress, some Republican lawmakers have been outspoken about their opposition to sending more money abroad. While it was not immediately clear if Mr. Zelensky’s pleas had changed any of their minds, he did take home at least one significant boost: a pledge to supply Ukraine with an advanced Patriot air-defense system, which will improve Ukraine’s ability to counter the missiles and drones that Russia fires at the nation’s energy infrastructure, deepening the suffering of civilians as temperatures dip during the winter.

“If your Patriots stop the Russian terror against our cities, it will let Ukrainian patriots work to the full to defend our freedom,” the Ukrainian leader said in his speech to Congress. “When Russia cannot reach our cities by its artillery, it tries to destroy them with missile attacks.”

The trip, a risky gambit coordinated in stealth, was also a projection of strength and confidence amid the daily blare of air-raid sirens from Russian attacks and persistent power outages.

“Each word was charged with Ukraine’s overwhelming energy and spirit,” Ukraine’s foreign minister, Dmytro Kuleba, wrote on Twitter. “May it inspire millions of people in the U.S. and around the globe to protect what we all hold dear: freedom.”