Editing Smoke signal (section)

==History and usage==
In [[History of China#Ancient China|ancient China]], soldiers along the [[Great Wall]] sent smoke signals on its [[beacon]] towers to warn one another of enemy invasion.<ref name=":4">{{Cite book|last=Ivan|first=Djordjevic|url=http://worldcat.org/oclc/699999686|title=Coding for Optical Channels.|date=2010|publisher=Springer US|isbn=978-1-4419-5569-2|pages=2|oclc=699999686}}</ref><ref name=":5">{{Cite journal|last1=Du|first1=Yumin|last2=Chen|first2=Wenwu|last3=Cui|first3=Kai|last4=Guo|first4=Zhiqian|last5=Wu|first5=Guopeng|last6=Ren|first6=Xiaofeng|date=2021-02-16|title=An exploration of the military defense system of the Ming Great Wall in Qinghai Province from the perspective of castle-based military settlements|url=http://dx.doi.org/10.1007/s12520-021-01283-7|journal=Archaeological and Anthropological Sciences|volume=13|issue=3|page=46 |doi=10.1007/s12520-021-01283-7|bibcode=2021ArAnS..13...46D |s2cid=231940516|issn=1866-9557|url-access=subscription}}</ref> The colour of the smoke communicated the size of the invading party.<ref name=":4" /> By placing the beacon towers at regular intervals, and situating a soldier in each tower, messages could be transmitted over the entire 7,300 kilometres of the Wall.<ref name=":4" /> Smoke signals also warned the inner castles of the invasion, allowing them to coordinate a defense and garrison supporting troops.<ref name=":5" />

Misuse of the smoke signal is traditionally considered to have contributed to the fall of the [[Western Zhou dynasty]] in the 8th century [[BCE]]. [[King You of Zhou]] was said to have had a habit of fooling his warlords with false warning beacons to amuse [[Bao Si]], his concubine.<ref>{{cite book |author=Sima Qian |author-link=Sima Qian |title=[[Records of the Grand Historian]]|volume=4}}</ref>

During [[Sri Lanka]]'s [[Kandyan period]], soldiers stationed on the mountain peaks alerted each other of impending enemy attack (from [[English people|English]], [[Dutch people|Dutch]] or [[Portuguese people]]) by signaling from peak to peak. In this way, they could transmit a message to the King in just a few hours.<ref name="Kandy 1681/2004">{{Gutenberg |no=14346 |bullet=none |last=Knox |first=Robert |title=An Historical Relation of the Island Ceylon in the East Indies Together with an Account of the Detaining in Captivity the Author and Divers other Englishmen Now Living There, and of the Author's Miraculous Escape |publisher=Project Gutenberg |year=2004 |orig-year=1681 |oclc=703947445}}</ref>{{failed verification|date=August 2024}}

[[Indigenous peoples of the Americas#North America|North American indigenous peoples]] also communicated via smoke signal. Each [[tribe]] had its own signaling system and understanding. A signaler started a fire on an elevation typically using damp grass, which caused a column of smoke to rise. The grass was taken off as it dried and another bundle was placed on the fire. Reputedly the location of the smoke along the incline conveyed a meaning. If it came from halfway up the hill, it signaled that all was well; but from the top of the hill, it signified danger.<ref>{{Cite web |title=Smoke Signal |url=https://addpmp.slamjam.com/index/smoke-signal |access-date=2022-09-13 |website=addpmp.slamjam.com |language=en}}</ref>

Colored [[smoke grenade]]s are commonly used by military forces to mark positions, especially during calls for artillery or air support.

Smoke signals may also refer to smoke-producing devices used to send [[distress signal]]s.<ref>{{Citation|title=Pyrotechnic device|date=Feb 4, 1964|url=https://patents.google.com/patent/US3120183|issue=US3120183 A|access-date=2017-02-01}}</ref><ref>{{Citation|title=Smoke signal|date=Nov 28, 1967|url=https://patents.google.com/patent/US3354829|issue=US3354829 A|access-date=2017-02-01}}</ref>