World War II: Filipino troops of the Philippine Commonwealth Army liberate the captured in Ilocos Sur and start the Battle of Bessang Pass in Northern Luzon.

The Philippine Army (PA) is the main, oldest and largest branch of the Armed Forces of the Philippines (AFP), responsible for ground warfare. As of 2021, it had an estimated strength of 143,100 soldiers The service branch was established on December 21, 1935, as the Philippine Commonwealth Army.

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, while Candon is the most-populous city. 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.

The Battle of Bessang Pass was a major battle during the Philippines Campaign of World War II. It was fought from 9 January through 15 June 1945, Cervantes, a municipality in the province of Ilocos Sur, located 382 kilometres (237 mi) north of Manila. The area serves as a gateway to the Cordillera mountains and the city of Baguio. Bessang Pass was a stronghold of the Japanese imperial forces under Gen. Tomoyuki Yamashita, known as the “Tiger of Malaya” and conqueror of Singapore. It was part of the triangular defense of General Yamashita in the north, namely the Balete Pass, Villaverde Trail and Bessang Pass, guarding the Ifugao-Benguet-Vizcaya borders. Its fall at the hands of the United States Army Forces in the Philippines - Northern Luzon (USAFIP-NL) on June 14, 1945 paved the way for the entrapment of Yamashita’s forces in the Cordillera until the general’s surrender in September 1945.

Luzon is the largest and most populous island in the Philippines. Located in the northern portion of the Philippine archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as well as Quezon City, the country's most populous city. With a population of 64 million as of 2021, it contains 52.5% of the country's total population and is the 4th most populous island in the world. It is the 15th largest island in the world by land area.