The army returns to Iraq where 179 British soldiers were killed between 2003 and 2011. Now they're helping the Iraqis defeat the so-called Islamic State. As the battle for Mosul begins the regiments operate behind the frontlines.

The army is sent to Estonia, on the frontlines odd a new cold war. As Russia flexes it's muscles in Ukraine and there is a buildup of troops across Eastern Europe, the risk of miscalculation is very real. Can the British army deter Russia expansion?