Notre Dame plays Navy every year as a tradition and a thank you for the U.S. Navy's crucial support during World War II, when the Navy used Notre Dame's campus as a training facility, providing vital income that kept the university financially afloat during a period of low enrollment. This established a debt of honor, creating a unique rivalry built on mutual respect, with Notre Dame committing to keep Navy on its football schedule indefinitely as repayment, making it the longest-played intersectional rivalry in college football.