The Challenger 2 OES is a modification for the Challenger 2 tank made to improve its survivability in high intensity battles. With the introduction of ERA blocks covering the sides and front of the vehicle, this protection was meant to deal specially with RPGs and ATGMs in urban combat. The vehicle also received updated protection against IEDs. The upgrade started development based on the Challenger 2 TES, which is almost identical; this upgrade was created as a response to the asymmetric warfare scenario of Iraq 2002, in which IEDs and urban combat doomed many NATO tanks due to their poor protection on the sides. The US developed a similar upgrade with the TUSK ERA package for their M1 Abrams tanks.

Introduced in Update "Air Superiority", the Challenger 2 OES is very similar to other Challenger 2 tanks. However, the increased weight due to the ERA and added composite screens does not include an upgraded engine, which means that the mobility of the Challenger 2 OES is mediocre when compared to earlier Challenger 2s. However, this comes with increased protection against both APFSDS projectiles and ATGMs, the ERA and composite screens are enough to increase the protection against other tanks in critical areas, while they also increase the chances of enemy ATGMs not penetrating the vehicle on the sides of the tank and the turret. However, the weak spot in the lower front plate is still present so take that into consideration and hide your hull whenever possible.