It was modified to defend against small arms fire and rocket-propelled grenades (RPGs) and therefore most of the weaponry such as machine guns and smoke grenade dischargers is on the top of the vehicle (1).

BBC: Factfile: Viking armoured vehicle

"Recent Mexican army and police confrontations with drug cartels have resembled small-unit combat, with cartels employing automatic weapons and grenades, " the advisory reads.

CNN: Commentary: What Mexico's drug war means for U.S.

On that morning, Staff Sergeant Romesha and his comrades awakened to an attack by an estimated 300 enemy fighters occupying the high ground on all four sides of the complex, employing concentrated fire from recoilless rifles, rocket propelled grenades, anti-aircraft machine guns, mortars and small-arms fire.

WHITEHOUSE: The White House

"Recent Mexican army and police force conflicts with heavily armed narcotics cartels have escalated to levels equivalent to military small-unit combat and have included use of machine guns and fragmentation grenades, " said the warning issued last month.

CNN: 2 top Mexican police officials killed in 2 days