In the later system the front ranks locked shields and presented a hedge of thrusting spears whilst the rear ranks kept up a continual barrage of missiles over the heads of the front rankers.
The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels.
Survivors said many workers were trapped in the multistory building because the access to the roof was locked and most windows were secured by metal grilles. From Karachi, Orla Guerin reports.