It was after the second quarter of the game at the Yale Bowl, New Haven, Connecticut, when scores of protesters from both colleges stormed the field, carrying banners and placards that accused the two prestigious universities of being "complicit in climate injustice" by investing in fossil fuel companies.
A few dozen protesters initially trickled onto the field as the Yale band finished performing its halftime routine.
Such signs were also attached to a chant of, "Hey hey, ho ho, fossil fuels have got to go".
According to The Crimson, the protesters entered the field without about three minutes remaining in halftime, and stalled the start of the third quarter by about a half hour.
TIME reports that when it came time for the game to resume, officials began making announcements over the PA system: "As a courtesy to both teams, the game must resume".
Protesters from climate advocacy groups at both schools flooded the field to force the game to be stopped.
With Yale hoping to clinch an Ivy League title, Harvard led 15-3 at halftime. Another read, "This is an emergency". An agreement was reached to escort the remaining protesters off the field, with one police officer to accompany every two protesters.
"While I respect the rights of Harvard and Yale students to protest, their efforts should not impact their fellow students' ability to pursue their passions as athletes on the field of play, and those who support them", Yale athletic director Vicky Chun said. Rachel Sadoff, a junior at Harvard, said about 150 students from the two universities planned to participate and about 100 more who had been sitting in the stands joined in.
The protest delayed the football game, which was being aired live on ESPN, for almost an hour.
Yale spokeswoman Karen Peart said the university agrees with an Ivy League statement that the protest's timing was "regrettable".
After about an hour, police formed a line and moved forward from the Yale sideline toward the Harvard sideline. "Harvard-Yale Game is literally peak establishment-and they were forced to think about what their investments are doing to the world".
Combined, Yale and Harvard have endowments of close to $71 billion, and numerous assets that make up those funds, demonstrators said, come from sources they find immoral.