Michael Codner, director of military studies at RUSI, says there is always a limit to capabilities and when soldiers are on the offensive trying to seize territory, you always want more.
BBC: Helicopters 'are no magic wand'
2.
Codner points to the Persian empire which extended over Afghan soil in the 18th century, having contributed to the collapse of the once-mighty Kabul-based Mughal empire that reigned over the region two centuries earlier.
CNN: Is Afghanistan really a 'graveyard of empires?'