This is a Merkava tank of the Israeli Defense Forces.
The tank has a rather exposed rear turret bustle, and the fear was that rocket projectiles such as RPG warheads might jam the turret. The chains were installed to detonate or otherwise reduce the likelihood of such effects. Because they are heavy steel balls hanging on chains they are more flexible than the rigid slat armour found in other armored vehicles used for the same purpose.
![](https://s2.save4k.ru/pic/PtWrDyFN6Cs/maxresdefault.jpg)