"There was only occasional gunfire."

Beg to differ, wwh.

Your variation does not describe the relative quiet in Fallujah as accurately as "gunfire was largely silenced".

What is being described is not a random lull in the fighting, but a silence imposed by the threat of imminent reprisals or by actual reprisals.

Sad to say, but no-one thinks this quiet will be "silenced" for long.