A group of Commando gunners are in California to brush up their skills with their US Marine counterparts. One-Four-Eight Battery of Two Nine Commando is one of the most specialised units in the Royal Artillery.
There's a steady trickle of people from this small, select group into the special forces. In the last in the series, John Andrews joined the teams, who get close to the enemy to call in artillery and air strikes, as they learned the art of concealment.
A specialist team from Two-Nine Commando, the Army gunners based in Plymouth, are on exercise in California. They've been working alongside US Marines in temperatures in the high thirties, nearly 100 degrees fahrenheit.
Our defence correspondent John Andrews joined them at the huge base on the coast near San Diego.