Vietnam-era Navy SEAL Roger Hayden, who spent ten days with the Australian Special Air Service during a mission in Vietnam, says that training in Australia taught him more about reconnaissance than anywhere else in the world. And for that entire ten days, the Aussies didn’t say a word. They just used hand and arms signals. Without having much preparation, they did dartboard ops where they threw a dart at a map and went to the location it landed. Because they had no intel or aid, they remained quiet for the entire mission.