Julian Chase was born and raised in New York City, a Polity protected zone. He lived with his mother, Roberta Chase, and sister, Driana Chase. His parents were both police officers in the New York City Police Department. His father was killed in the line of duty when Chase was young, though his mother made it to retirement. At some point, Chase left New York to join the Vanguard, which required the Weller test among other screenings, which identified him as gen:LOCK compatible. In the Vanguard, he became an Interceptor pilot rose to the rank of first lieutenant, and was stationed at the Anvil.
In 2068, Chase visited his mother and sister via Mixed Reality with his girlfriend Miranda Worth moments before the Union attacked the city. Colonel Raquel Marin sent a battle group from The Anvil to defend the city, and Chase was among the pilot's in an Interceptor squadron. While he evaded Union drones and fighters, the Union wreaked havoc at ground level with its Nanotech, severely hindering the Vanguard's efforts to aid the citizens and repel the Union, killing many. When a Behemoth appeared near the city, Chase decided to risk his life and detonate his ESD even though Simone Rasmussen's attempt resulted in her death. Though he successfully discharged his ESD, he had used his Interceptor to shield it from the Behemoth's anti-air fire and it lost a wing in the process.
Without the ability to eject, Chase crashed with his aircraft. The public presumed him dead, but he clung to life, and the Polity rescued him and placed him in the Experimental Science Unit, as he was one of its most important soldiers. Having suffered grievous injuries, he was put in a preservation tank where he could achieve gen:LOCK, having agreed to the program.
While he was on a mission, the Union captured Chase, whose mind was still trapped within the prototype Holon. After fruitlessly attempting to find and rescue Chase, Weller put a second digitized copy he had been compiling of Chase's brain back into his body. To Chase, he was offline for a few hours and never went on the mission. After this, no more copies of Chase's mind were made and Weller had no intention of making copies of the minds of future gen:LOCK pilots. Chase continued to work under Weller, eventually working alongside Yasamin Madrani before being stationed back at the Anvil.