Враг вступает в город, пленных не щадя

По наводке fat_yankey нашел несколько менее драматичный оригинал перевода Маршака.

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.