He began his career in the 26th Infantry Battalion, of the
4th Infantry Division, and also led troops during communist insurgents in 1988 at the
Agusan Provinces. He also led the 52nd Mechanized Infantry Company of the
Light Armor Brigade during the
Battle of Camp Abubakar as part of the
"All Out War" Operations against the MILF in 2000. He also led the
3rd Mechanized Infantry Battalion on combating communist insurgents in
Central Luzon. He commanded various units in the
Philippine Army and other AFP units deployed in major areas in
Luzon and in
Mindanao, primarily specialized in infantry and mechanized cavalry operations. He also led diverse units and was assigned to different areas in the AFP, such as in intelligence, education and training, civil and military operations and joint operations. He became deputy commander of the
Eastern Mindanao Command (EastMinCom), based in Davao City; commander of Joint Task Force Haribon which secured Davao City and the rest of Davao region during the
2016 Davao City bombing, and also became the military spokesperson of the
martial law implementation in Mindanao. He also served as the Chief of Staff of the Philippine Army in 2016, where he earned his second star (
Major General), and commanded the
Armor “Pambato” Division (formerly the Mechanized Infantry Division) in 2017. As commander of the Armor Division, he spearheaded the modernization of the army's armor and aviation units, and laid out future acquisition programs for the army's new assets, such as the conversion of 5
M113A2 APCs to
self-propelled mortar systems equipped with the
Cardom system, and the procurement of the army's Elbit UAVs, and upcoming armor and aviation assets. He became commander of the
Southern Luzon Command (SoLCom) in January 2019, where he earned his third star (
Lieutenant General).He was also responsible in the successful launching of the Philippine chairmanship of the
ASEAN in Davao City and the successful conduct of high-level ASEAN meetings and major international events. Noteworthy was the “zero incident” of terrorism during his tenure. He also oversaw the 2019
Balikatan exercises as the country's exercise director. On December 6, 2019, he was named as the new
Commanding General of the Philippine Army, where he replaced his classmate, Lieutenant General
Macairog Alberto, after reaching his mandatory retirement age at 56. As Chief of the Philippine Army, he oversaw all army operations amidst the
COVID-19 pandemic and spearheaded the army's modernization programs, which delayed and limited the other acquisition programs that were laid out by the Army. Nevertheless, the Army still procured new and modern assets that is set to upgrade the army's capabilities, such as the
GDELS ASCOD Sabrah light tanks, which also includes an armored command vehicle, and an armored recovery vehicle; the
Excalibur Army Pandur II tank destroyers and command vehicles, and the
Iveco VBTP APCS. On July 29, 2020, he was named as the new
Chairman of the Joint Chiefs, the highest post in the AFP, and took helm on his post on August 3, 2020, replacing his classmate
Felimon Santos Jr. Gapay is the 54th AFP Chief of Staff, and the 8th under Duterte's administration since 2016. He earned his fourth star, and was promoted to the rank of General on October 7, 2020. He retired from military service on February 4, 2021, after reaching the mandatory military retirement age of 56. He was replaced by the
Chief of the Philippine Army and
Medal of Valor awardee, Lieutenant General
Cirilito Sobejana. ==Awards and decorations==