How does frequency-hopping spread spectrum help protect military radio transmissions?

Frequency-hopping spread spectrum (FHSS) is a vital electronic protective measure used in military communication to counter electronic warfare tactics, specifically jamming and eavesdropping.1

The technique protects transmissions by rapidly switching the radio frequency channel according to a specific, prearranged pattern known only to the authorized transmitter and receiver. Because the signal does not remain on a single frequency for long, it becomes significantly more difficult for an adversary to successfully jam the communication or intercept the transmission for signals intelligence purposes. By constantly changing channels, the system effectively undermines enemy attempts to deny or monitor the use of the electromagnetic spectrum.1