“Guerrilla warfare is a form of warfare by which the strategically weaker side assumes the tactical offensive in selected forms, times, and places.” Dr. Samuel Huntington
The differences between conventional and unconventional warfare are numerous, however the most obvious is the fact that irregular/unconventional/guerrilla warfare pits a strategically more powerful conventional army against a weaker enemy force – weaker in personnel, materiel, technology, weaponry, etc. Historically, conventional armies have attempted to use their tried and true conventional warfighting methods such as the use of massive firepower and operational maneuver, while a guerrilla force will avoid fighting in the open (because they know it will lead to its annihilation) and only engage in situations carefully selected to give them a tactical advantage. In one of the most prolific works on the topic of guerrilla warfare Ernesto “Che” Guevara recognized it as the most effective means of combating “large concentrations of enemy forces” which would be forced to deal with “a mobile, impenetrable, gelatinous mass that retreats and never presents a solid front, while inflicting wounds from every side.”
Mao Tse Tung for his part believed that guerrilla style warfare was a useful tool, however he believed it was “a necessary strategical auxiliary to orthodox operations.” Mao seems to put less stock in guerrilla warfare being able to help the win a strategic victory on its own – and he was correct to an extent in this. In many of the historical examples in which the “weak” defeated the “strong” through unconventional methods, the “weak” had to rely on the assistance of other “strong” conventional powers. The Viet Cong had the NVA as well as assistance from China, the USSR and the many Soviet bloc countries who supplied them. In the American Revolution the U.S. had France, the 1980s Mujahideen in Afghanistan had the support of the U.S. against the Soviets. In Syria’s recent war various factions were backed and supplied by Russia, Iran, or the U.S. Today Ukraine, a much smaller country with limited means, is being supplied with an array of weaponry from NATO nations – and apprears to be grinding down the much larger Russian Federation forces. Small units of Ukrainian soldiers with shoulder fired anti-tank and surface to air missiles have wreaked havoc on enemy supply lines and made widows of many Russian close air support aviators.
One can also point out historical examples of insurgencies that failed due to the lack of support from a stronger conventional ally. The Jewish revolt of 66-70 AD is an example from antiquity. They inflicted some serious damage on the Roman legions but lost the war. More recent examples include the failed communist insurgencies in Guatemala (1960-1996), El Salvador (1980-1992), and Colombia (1964-2016) due to lack of adequate support from their communist benefactors.
On a side note, not directly related to this topic, Mao’s work on guerilla warfare is interesting, he wrote it in 1937 with emphasis on using guerrilla tactics to fight the Japanese. However, in the years immediately following its publication (1937-1940) he did everything he could to avoid fighting the Japanese, much to the frustration of Stalin and the USSR who wanted him to tie up the Japanese in China as much as possible. Instead of fighting a guerilla war against Japan, Mao spent his time fighting against rival communist leaders and Chiang’s nationalists. In their 2005 work Mao: The Unknown Story Julie Chang and Jon Halliday included a whole chapter on this (Chapter 20). I read the book several years ago and highly recommend it if you are interested in recent Chinese history and Mao. It was an eye-opener for me.
 Max Boot, Invisible Armies: An Epic History of Guerrilla Warfare from Ancient Times to the Present (New York: Liveright Publishing Kindle Edition, 2013), Kindle Locations 302-303.
 United States Department of Defense, Department of the Army, Field Manual No. 3-24 Counterinsurgency, by Lt. General David H. Petraeus and Lt. General James F. Amos (Washington, DC: Department of the Army, 2006), 11.
 Ernesto “Che” Guevara, Guerrilla Warfare: Authorized Edition (New York: Ocean Press, 2006), 141-142.
 Mao Tse-Tung, Mao Tse Tung on Guerilla Warfare, trans. Brig. General Samuel B. Griffith USMC Ret. (Hauraki Publishing. Kindle Edition, 2014), Kindle Locations 628-630.
 Boot, Invisible Armies. Kindle Locations 431-464.