Armored personnel carriers (APCs) and Infantry Fighting Vehicles (APCs with more armor and a turret carrying a weapon that can destroy an APC or IFV) were originally designed to help infantry keep up with tanks while providing protection from machine-guns and artillery fragments. The most successful APC, the American M-113, had armor that kept out rifle and light machine-gun fire, as well as some heavy machine-gun fire (12.7mm/.50 caliber). But the Soviets were putting 14.5mm machine-guns on their APCs, and these could chew up a M-113. But eventually, an add on armor kit was developed and this protected the M-113 from 14.5mm bullets. In the 1980s, the M-2 Bradley IFV began to replace the M-113 in infantry units. This vehicle had better armor and could stop 14.5mm bullets, as well as fragments from larger (152mm) artillery shells. All U.S. armored vehicles also got lightweight Kevlar material inside the crew compartments to reduce injuries from bits of armor flying around when something did penetrate. The new medium brigades are using a wheeled APC, the LAV-25. But these only have the same armor protection as the original M-113. But like most American light armor, these vehicles can attach reactive armor (blocks of explosives) that protect against anti-tank rockets. These weapons (most frequently the Russian RPG series) are found all over the world and are the biggest danger to light armored vehicles. Many potential U.S. foes have Russian designed BTR (wheeled) APCs and BMP (tracked) IFVs. These have lighter armor than the M-113. They protect against rifle fire, but not from .50 caliber machine-guns.