sentences:  During Operation Protective Edge, the US authorized Israel to access 120mm mortar rounds and 40mm grenade launcher ammunition.These munitions were part of a set of older items in the stock, and were due to be replaced soon.In October 2012, United States and Israel began their biggest joint air and missile defense exercise, known as Austere Challenge 12, involving around 3,500 U.S. troops in the region along with 1,000 IDF personnel.