Valor day, also known as Araw ng Kagitingan or Bataan Day, commemorates the fall of Bataan, an important event in Filipino history. On the 9th of April 1942, during World War 2, Major General Edward P. King Jr. was forced to surrender his troops to the Japanese army. And it is one of the most-devastating military defeats in American history. The force on Bataan, numbering some 76,000 Filipino and American troops, is the largest army under American command ever to surrender.
Unprepared for the number of prisoners, the Japanese decided to walk the prisoners 150km to a prison camp in San Fernando. Over 20,000 prisoners died on this march either through starvation, exhaustion or at the hands of the Japanese. The trek became infamous as the 'Bataan Death March'.
For the whispered words, “Bataan has fallen,” which was beamed by a freedom radio station that fateful day, merely signaled the start of a liberation struggle that was to rank the Filipinos among the world's most intense and courageous freedom fighters. “Araw ng Kagitingan is relevant in our society, this week-long commemoration is an opportunity to remember not only Filipino war veterans who died or served their country, but also those who served honorably in the military in times of war or peace.
Sources:
https://www.timeanddate.com/holidays/philippines/araw-ng-kagitingan