When the Japanese invaded, the then colonial masters, the Americans, had declared Manila an open city to prevent damage and human casualties.
When the Americans along with support from local guerrillas moved on Manila to liberate it, the Japanese commander, Yamashita, ordered Manila to be fiercely defended. What followed was a liberation, almost building by building. However it was the Japanese treatment of the local population that was most horrific with estimates of 100,000 civilians being slaughtered. There is no true count however and other estimates are higher.
Review to follow when I finish reading this book. It is available from Pen & Sword however if your curiosity is already peaked.