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 message was lost.
For want of a message the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe nail.

— German proverb

Photo credit: The Portable Antiquities Scheme/ The Trustees of the British Museum [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)%5D