How did Philippines hold for a while during WW2?

Quite simply, the American and Filipino forces withdrew into the narrow, heavily jungled Bataan peninsula, significantly reducing the frontage they would have to defend, thereby limiting the amount of force that the Japanese could employ. Both flanks were thus anchored on the sea, making it virtually impossible for the Japanese to outflank the much smaller force, and the added obstacle of the jungle acted as what in the military is called a "force multiplier." This means that the highly defensible terrain that the Filipino-American forces occupied served to increase the effectiveness of the defense, as if they had had more troops than they actually did.

This is a classic military maneuver. The Spartans at Thermopylae adopted the same tactic, as did Henry V at Agincourt, to name only two notable examples of this technique having been employed throughout history. Sometimes it can result in victory, as at Agincourt, and sometimes the result is defeat, as in the Philippines and at Thermopylae. But even in the latter two cases, the tactic significantly delayed the attacker, and in the latter case this delay allowed the Greeks time to assemble an army and a fleet that eventually defeated the Persians.

held key points in jungle areas - like bataan and correigador - American Troops had alot of supplies as always - at the beginning of hostilities - the troops lasted longer than supplies as the Filipino Troops did - they were led and inspired by US Officers and the command structure - as sea lanes were cut off by the japanesse navy and airforce the troops ran out of food and ammunition - casulties were heavy - malaria was spreading and medical supplies had ran out - General Macarthur was ordered by President Roosevelt to leave and go to Australia to avoid being captured by the Japanese - though outnumbered heavily by the Japanese US forces were able to hold out long with better planes - leadership - logistics and intel - though this was ground down against relentless attacks by overwhelming numbers of Japanese - after the surrender the Japs sent the starving and sick American Troops on the ' Bataan Death March ' soldiers that fell were beaten to death by Japs or left to die - the soldiers marched without food or water and dropped and died in the sun while the japs ate well and inflicted horrible crimes bayonetting soldiers chopping off heads - american officers were treated as bad as the soldiers - the japs did not distinguish rank

Retreating to what they thought was a defensible position and holding out there as long as they could.

The time honoured scorched earth policy