"We have dramatically improved in the last year, and the proof is in how much ground ISIS has lost," Kaine, the Virginia senator who is Hillary Clinton's running mate, told CNN's Jake Tapper Sunday on "State of the Union."
"A year ago, I think you remember, we had a small force that we were trying to put into Syria, and the opening of that was an abysmal failure," Kaine said.
"But now we are taking the fight to ISIS to defeat them and to destroy them. And if you look at what's happened in the last year, ISIS's territory has dramatically shrunk because of a significant uptick in cooperation between the US, the Iraqi military, the Kurdish fighters in northern Iraq, the Kurds in northern Syria and the Syrian opposition. We're shrinking their space on the battlefield," he said.
Kaine blamed Syrian President Bashar al-Assad for Syria waging "a war against its civilians," creating an opening for ISIS, and said Russia will play a key role in the country's efforts to combat ISIS.
Kaine also pushed back on questions about whether the United States' decision to pull troops out of Iraq under President Barack Obama allowed for the rise of ISIS, saying that leaders there didn't want the US to stay.
"We pulled our troops out of Iraq because they didn't want us to stay. And yes, in Iraq, it spiraled downward," Kaine said. "And then in Syria, where we didn't have troops, it spiraled downward because of the atrocities of Bashar al-Assad."
He added: "We can't make governments govern wisely. But what we need to do is when terrorists pose a threat to allies of the United States, we need to engage in punishing activity to destroy them. We are now on track to defeat ISIS on the battlefield, but we have got to be sharing intelligence with our allies so that we can keep America and our allies safe."
The Trump campaign rebutted Kaine's comments, saying: "The only thing that is 'dramatically improved' is ISIS's global reach, the frequency of deadly attacks, and the threat they pose due to the failed national security policies of President Obama and Hillary Clinton."
"Given that recently uncovered U.S. intelligence documents say ISIS is expanding the number of areas where they are fully operational, Hillary Clinton should say whether she agrees with her running mate's troubling assessment of the threat they pose," Jason Miller, a spokesman for Donald Trump said in a statement.