The Mark IV is the most recent variant of the Merkava tank that has been in development since 1999 and production since 2004. The upgrade's development was announced in an October 1999 edition of the Bamachaneh ("At the Camp") military publication. However, the Merkava Mark III remained in production until 2003. The first Merkava IVs were in production in limited numbers by the end of 2004 When ammunition is unloaded the tank can carry up to 8 dismounted soldiers or 3 stretchers. Troops enter and leave the vehicle through the rear hatch. Removable modular armor, from the Merkava Mark IIID, is used on all sides, including the top and a V-shaped belly armor pack for the underside. This modular system is designed to allow for damaged tanks to be rapidly repaired and returned to the field. Because rear armor is thinner, chains with iron balls are attached in order to detonate projectiles before they hit the main armored hull