The Battle of Tirad Pass, sometimes referred to as the "Philippine Thermopylae", took place during the Philippine–American War on December 2, 1899, in northern Luzon in the Philippines. A 60-man Filipino rear guard commanded by Brigadier General Gregorio del Pilar succumbed to more than 500 Americans, mostly of the 33rd Volunteer Infantry Regiment under Major Peyton C. March, while delaying the American advance to ensure that President Emilio Aguinaldo and his troops escaped.

Ilocos Sur, officially the Province of Ilocos Sur, is a province in the Philippines located in the Ilocos Region in Luzon. Located on the mouth of the Mestizo River is the capital of Vigan. Ilocos Sur is bordered by Ilocos Norte and Abra to the north, Mountain Province to the east, La Union and Benguet to the south and the South China Sea to the west.