I'm choosing both Juicer Uprising and Tolkeen siege.
Jack Powers wanted to believe.
He...didn't actually know what he wanted to believe -in-. But he knew once he found it he'd know!
At first he thought it was Government. He joined the army in the name of the Glorious Name of Emperor Karl Prosek. He was given training and gleefully marched in the name of the Campaign of Unity!
Many filthy Shinies (their name for the magic-touched) did he bring salvation to. (All souls call out for salvation--though the currently preferred method was death.)
His first real test came at the Netwon Incident, also called the Juicer Uprising. He personally guarded the left flank while the Doomsealer panzers crashed against the command squad of the enemy.
Although he was no where near Newton when it went critical, the "outsider involvement" did inflict heavy casualties against his unit. Only the quick action by the apothecary saved his life.
His body--once a meat-packed specimen of pride--was now metal and ceramics. They took away his name and gave him a new designation. He liked it. It sounded impressive. The power of the new body was...intoxicating.
He reveled in the new upgrades! Able to run almost without fatigue, and carry a massive amount of gear, he re-joined his re-built unit as hero!
He continued in the Campaign determined that he had found his cause!
For another four years he brought glory and honor to the name of the Emperor, until...
He was on the front lines at Tolkeen. Chiefly engaged in mobile-reserve and suppression of counter-attacks, he ran all over the battlefield, making sure the dirty, dirty Shinies received the salvation they so richly earned!
On the last day, when both flanks collapsed and the glorious army moved forward...he saw...her.
An older female, probably her mother, helped her into a panzer...a suit of power armor the glory hounds--or "Glitter Boys" as they called themselves--used. The panzer ran to the South, while the older female rushed into a building, for some reason. He ran after her, but the air strike had already been called.
Jack was caught in the explosion.
When he regained consciousness the world had...changed. Or rather he had. Many of his memories were like displays caught behind foggy glass.
As we walked to join his unit, he feet turned south.
He had found something to believe in.
He found out her name was Jonis. He didn't know that she would at Castle Refuge, but the tide of refugees from Tolkeen was heading there.
So was he.