Your team is deployed by Captain Acheran to Kadaku to defend and ready the Cadian 8th for the invasion. After a few encounters while helping the Cadians set up weapons for defense your team spots an inquisitorial dropship under attack and crashes. Captain Acheran directs you to proceed to crash site and search for survivor's the crash site is located near a suborbital launcher upon arriving your team defends the sole surviving inquisitorial agent. 

This would set your team up to being the one that rescued Titus.

https://community.focus-entmt.com/focus-entertainment/space-marine-2/ideas/9425-idea-prequel-operation?page=1#post-9425