While making the case for Harris as commander-in-chief, Leon Panetta, the Secretary of Defense under former President Barack Obama, said Trump will "abandon our allies and isolate America."

"Listen to President Reagan," Panetta said. "Isolationism never was and never will be an acceptable response to tyrannical governments."

In drawing a comparison between the two candidates, he said, "Trump tells tyrants like Putin they can do whatever the hell they want. Kamala Harris tells tyrants the hell you can. Not on my watch."

He drew the largest applause when he said that the role of the U.S. military is to defend us from foreign enemies and "sure as hell isn't to put immigrants in camps."

Rep. Ruben Gallego, an Iraq war veteran, brought on stage Democratic veterans serving their county and in elected offices at every level.

"These veterans represent the best of our country," he said. "We stand united as veterans, Democrats and patriots to fight for everyone who serves."

"But politicians like Donald Trump. They don't stand with us," he said. "They call patriots like Sen. McCain 'losers.' John McCain was an American hero. Show some respect."

Gallego is running for Senate in Arizona against Trump-ally Kari Lake.

The vice president’s motorcade arrived at the United Center at 9:48 p.m. ET, according to the press pool.

Another sign of how Democrats are trying to turn patriotism and national security arguments on their head, is the prime-time speaking spot for Leon Panetta -- telling the story about giving the order that led to the death of Osama bin Laden.

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Leon Panetta warns of ‘moment of danger’ during full speech at the DNC

The former U.S. Secretary of Defense said, “We need Kamala Harris behind the resolute desk.”

-ABC News' Rick Klein