Why are troops instructed to break step when they are marching over a bridge?

Name: Why are troops instructed to break step when they are marching over a bridge?
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Question

Quizplus · Accepted Answer

The Answer is If all the soldiers march in step,a single frequency disturbance is applied to the bridge.If that frequency coincides with a natural frequency of oscillation of the bridge,a large amplitude response is possible.By breaking step,the driving force will have many random frequencies of smaller amplitude.

Why Are Troops Instructed to Break Step When They Are