President Trump is trying to apply enough pressure to force the university to cave, while Harvard, a nearly 400-year-old institution, is aiming to play a long game against an aging president in his final term.

The U.S. State Department ordered all its consular missions overseas to begin additional vetting of visa applicants looking to travel to Harvard University for any purpose, according to an internal cable seen by Reuters on Friday,

As the legal battle between the Trump administration and Harvard heats up, here's a look at what Harvard calls Trump's "campaign of retaliation" against the school.