"Way to die on the job dipshit.."
-Jack to a fallen foe
Spartan-IV Jack Delrio is Fireteam Sabers combat engineer. He is still serving with them and goes by the call sign, Saber 3.
Born and raised on mars, Jack grew up with a military family. His father, an ODST, and his mother, a corporal in the UNSC Marine Corps, we're both listed as K.I.A. He wanted to follow his parents footsteps by becoming a soldier. He enlisted as a Spartan-IV and trained to become a UNSC super soldier. He was trained with heavy weapons and as well as vehicles. He served in many battles including Battle for earth, OrionIV, Requieum.
Later in his life, he went to Traning. He got along with most recruits. But he got along very well with Alyssa Romero, a fellow spartan and later teammate. They would always run courses together. Eventually they fought on the battlefield together.
On October, 20th, 2558, Jack was reassigned to FireTeam Saber. There, Alyssa Romero, a fellow friend and teamate, fell in love with him. Though she kept it a secret, he knew that she loved him. He proved useful for the team but was always late when they really needed him.