GRENADE SURPRISE AT WW2 D-DAY BUNKER One of the deadliest secrets on some of the bigger bunkers in Normandy is the anti-grenade design of ventilation systems. Anyone assaulting this position and dropping a grenade into the vents would be in for a big surprise. Instead of falling inside the bunker, the construction meant that explosives would fall at the feet of the attackers. This was due to the simple, but clever Y-shaped design of the pipe work which allowed air to circulate through to an inte