On 10 May—code-named Q-Day—the 108th joined in the battle for Mindanao. The regiment made an unopposed landing at Macajalar Bay near Bugo and moved south to clear the Sayre Highway with the assistance of Filipino guerrillas. From 13–18 May the 108th fought tenacious Japanese defenders at the Mangima River canyon, which became known as Purple Heart Canyon. The regiment linked up with the 31st Infantry Division coming up from the south on 23 May. Securing the Sayre Highway cost the 108th about 15 men killed and 100 wounded. (Non-combat casualties from battle fatigue, sickness, and heat exhaustion were probably heavier.) The troops then moved east to combat more Japanese resistance. After six weeks of enduring thick jungle, heavy rains, knee-deep mud, and tall, razor-sharp grass—not to mention Japanese resistance—the 108th rejoined the 40th Division on Panay. The 108th RCT lost 45 members killed and 148 wounded in northern Mindanao.