What is the main conflict in Separation of Power by Vince Flynn?

The Separation of Power is part of a series of espionage novels written by Vince Flynn. It continues the story of the counter terrorist, Mitch Rapp. Mitch is on the verge of retirement, but knows he cannot retire safely until he has found out who tried to kill him on his previous mission to Germany. However, his obsession only creates more problems for him, breaking up his relationship with Anna Rielly, getting him involved with the Israeli secret police and taking him on one last mission to destroy nuclear warheads in Iraq.