Here's every Game Of Thrones actor who played a major role on Strike Back. Strike Back was based on the Chris Ryan novel of the same name, and the series cast Richard Armitage and Andrew Lincoln as part of a British unit dubbed Section 20. The Sky produced series was an ambitious, globe-trotting action show that served as a good star vehicle for Armitage. While there were plans for Armitage's John Porter to lead season 2, fate had different plans in store.
Armitage's commitment to The Hobbit movies saw him become unavailable for Strike Back season 2. The show also became a co-production between Sky and American network Cinemax, which saw an increase in the amount of action and sex scenes. Philip Winchester and Sullivan Stapleton were cast as the new leads Stonebridge and Scott, and it became a big hit with action fans. This version of the series ran for four seasons before it later rebooted with a new team in 2017; this iteration lasted a further three seasons.
The second season Strike Back: Project Dawn is technically the first season in the U.S., and it aired the same year that Game Of Thrones debuted. One thing fans of both shows may have noticed as they evolved is that they shared a lot of actors, with Project Dawn alone featuring Liam Cunningham - AKA Ser Davos from Game Of Thrones - playing IRA terrorist Daniel Connelly, Adewale Akinnuoye-Agbaje as Tahir (who appeared briefly on GoT as Malko) and Ser Jorah himself Iain Glen as Gerald Crawford.
That said, both Cunningham and Akinnuoye-Agbaje appeared on Strike Back: Project Dawn before their Game Of Thrones debuts. Also, Alexander Siddig is technically the first major GoT performer to appear on both shows; he played Zahir Sharq in the first season of Strike Back before debuting in Game Of Thrones season 5. Roose Bolton performer Michael McElhatton later played guest villain Oppenheimer on Strike Back season 5, who had a dark history with Robson Green's Locke.
While the actors above all appeared on Strike Back for about two episodes max, Charles Dance was a major recurring villain on season 3 Vengeance. The Tywin Lannister actor played billionaire businessman Conrad Knox, who attempted to make South Africa a nuclear power, and he appeared in nearly every episode of that season. Given the insane amount of crossover between the shows, it only made sense that eventually a Game Of Thrones actor would be cast in a main role on Strike Back, with Roxanne McKee - who played Daenerys' handmaiden Doreah on the former's first two seasons - cast as Captain Reynolds in the latter's sixth season.