Dorey sailed with the regiment to Cuba in April 1898 during the Spanish–American War and took part in the Battle of El Caney and Siege of Santiago in July that year. He later took part in the Philippine–American War and served as 4th Infantry Regiment's Aide-de-Camp in the combat operations against Moros at Zamboanga and Manila. Dorey commanded as Captain the battalion of Philippine Scouts at Mindanao and was appointed Aide-de-Camp to Major general Leonard Wood, who served as the governor of Moro Province, a stronghold of Muslim rebellion. Dorey was decorated with his first Silver Star for his bravery on Philippines.