for want of a nail

A major catastrophe that can be traced back to a small error. The lack of a basic part or a small object can lead from one unwanted consequence to another larger one to yet another one, as in a stack of falling dominos. The full proverb is “For want of a nail the shoe was lost. For want of a shoe the horse was lost. For want of a horse the rider was lost. For want of a rider the battle was lost. For want of a battle the kingdom was lost. And all for the want of a horseshoe nail.”