He took part in many encounters with the Spaniards, particularly in engagements resulting in the deaths of his superior officers, such General Candido Tria Tirona, Edilberto Evangelista, and Crispulo Aguinaldo, which caused his rapid promotion.

[5] Cailles formed six military columns led by Lt. Col. Regino Diaz Relova (Pila, Bay, Calauan and Los Baños), General Severino Taino (San Pedro, Biñan, Santa Rosa, Cabuyao and Calamba), Lt. Canuto Aritao (Lumbang, Longos, San Antonio, Paete, Pakil and Pangil), Major Roman Dimayuga/Lt.

On September 17, 1900, Cailles' troops outmaneuvered and routed a strong American contingent led by a Colonel Cheetham during the Battle of Mabitac in La Laguna.

Magnanimous in victory, Cailles allowed Cheetham to recover the bodies of eight slain Americans from the field, together with all their personal belongings.

After serving as acting chief of operations in the first zone of Manila during the War, Cailles was appointed by Emilio Aguinaldo as military governor of La Laguna and half of Tayabas (now Quezon Province).

Aguinaldo's capture in Palanan, Isabela on March 23, 1901, convinced Cailles that the war was lost, leading to his own surrender to American troops on June 20.