Prior to his military service, Mr. Delollo received training in Game Theory & Holographic Cinema, and had a high retention rate for trivia. He has said of himself many times that he is a "Fountain of useless Knowledge".

Joining the Starfleet Marine Corps in 2347, Keith A. Delollo underwent standard basic training on New Paris Island and entered the service as a Private First Class. Advanced MOS Training included Recon, Combat Engineering, and Logistics. His first duty assignment was with the 86th MSG, First Squad, 2nd Fire Team, Recon.

During the Cardassian War, the 86th was stationed on Saris 3 near the Cardassian Boarder, as Embassy Marines while Ambassador Sarek was to conduct Peace Negotiations. In reality, the 86th was on mission to conduct "Operation Sleepy Weasel". Intell had found the Cardies had sent an assassination team in after the Ambassador, and Starfleet handed the intercept mission to the 86th. PFC Delollo's recon team found their base of operations the night before the assassination attempt, and without calling in support; killed most of the team while the slept, and captured their team leader. Later on that same year he was awarded the Starfleet Marine Award and given a promotion to Lance Corporal by Division Commander Major General Jackson. This occurred after DeLollo drew heavy fire in a diversion to save the 86th Command Staff, which was pinned down and in serious threat of being destroyed. By the time he ended his tour with the 86th, he held the rank of Sergeant-Major. It was at this time that his career started to turn heads.

In 2349 the Executive Officer of the 86th, First Lieutenant Thomas Gorman, was promoted to the rank of Captain and hand picked to command the brand new (at the time) 21st Marine Training Regiment. This regiment, stationed a mere week's journey from the most intense fighting, was created to give new Marines and Starfleet Security personnel a final opportunity to hone their skills at ground combat and starship boarding in hostile conditions. Gorman chose SGM Delollo to be his Regimental Sergeant Major, and together they established many of the rigorous field exercises used by Starfleet Marine instructors to this day. At the time, no one knew that this team would be such a driving force in directing the Federation Intelligence Community.

In 2354, RSGM Delollo was approached by an agent of the Special Security Division, and quickly recruited into that organization. Even though what he did for the SSD is classified, what is known is this; on 12 different occasions between 2354 and 2360, RSGM Delollo was requested for off base Recon Training Missions for the 673rd RMSG. There is no known listing for any 673rd RMSG anywhere in the Federation.

In 2360, 21st Regimental Commander Gorman, now a Major, was promoted to Lieutenant Colonel and given command of the 5th Division. Again, Gorman requested DeLollo to follow him into this new posting and so, RSGM Delollo took over the Divisional Sergeant-Major position. It was during his tour as DSGM that he became a curiosity for the Klingon Empire. While acting as Aide de Camp for LCOL Gorman at a State Dinner between members of the Klingon High Command and various Starfleet Command members, he uncovered a plot to start a war between the Klingons and the Federation. A member of the Klingon delegation (who turned out to be a Cardassian spy) tried to set off an Anti-Matter Bomb, and frame the Klingons for the attack. DSGM Delollo found the spy setting the bomb, incapacitated him, and deactivated the bomb. When news of this reached the members from both delegations he was approached by the Highest Ranking Klingon, a young General by the name of Martok. He asked what the Klingon Empire could do to show its appreciation, and in reply DSGM Delollo said "Well sir, I was hoping I could be seen as an equal in your Empire, I want to be assigned to a Klingon Marine unit." He was given that boon, on one condition; he had to prove himself worthy of the true warrior spirit of a Klingon. So for the next 6 months he underwent training as a Klingon Marine, ate Klingon food, and at the end of the training became the only human to ever go through and pass the "Klingon Right of Ascension". He proudly counts his own Klingon Pain Stick as one of his most prized possessions.

In 2365, returning from a successful tour of duty with the Klingon Defense Force, SGM Delollo was appointed to the post of Sergeant-Major of the Starfleet Marine Corps. As CSGM, he helped institute new NCO Training policies and would later team up with now Brigadier General Gorman in an effort to help bolster the flagging enlistment numbers that occurred after the tragic events of Wolf 359. It was as part of this elite team of Public Relations officers that he helped to boost recruiting and the Corps enjoyed a period in which its numbers swelled to record highs. By the time the Dominion War began, the Corps was more than ready to answer the call. In 2372 SGM Delollo retired from active duty, but still held a reserve status in case he should ever be needed again. He did not retire from active service from the SSD, however. He remained an agent in the field, and later was promoted into the Directorate.

In 2375, he re-entered active service in the Corps for a 1 year tour, to help establish the refitted Starbase Inchon as a training facility to be used by Starfleet and SSD personnel. The Base was commanded by Brigadier General Christopher Maxfield, of whom he knew only a little. DeLollo did find comfort in knowing that the base's Executive Officer was an old friend: Thomas Gorman, desirous of returning to duty, apparently accepted a two-rank demotion to Colonel (much to DeLollo's surprise) in order to work at Starbase Inchon. DeLollo could not help but reflect on how well his earlier recruiting efforts had to have worked in order for Gorman to be unable to return to duty at his former rank.

A mere two months after assuming his duties, the tragic events which led to Inchon's disappearance from the known universe occurred. It was at this time that COL Gorman informed BGEN Maxfield of his and SGM Delollo's true identities. In fact, they were the Heads of the SSD, and were there to see the final installation of a forward listening post into Cardassian space, to be placed onboard the station.

For the past year, SSD Deputy Director DeLollo, has been helping the newly formed Galactic Military Force Command integrate alien and Federation technology into the few ships that GMF has on hand.