Having eyes on the battlefield can mean the difference between hitting the right or wrong target, or even hitting the target at all, which is why U.S. special operators are looking to upgrade a host of optics items.
For ground-based observers calling in fires on a target, the observer historically worked with a radio and a pair of binoculars, or a bulky laser guidance system to get the job done. But systems have become more more precise and portable over the decades.