Guerrilla warfare is basically 'Hit and Run' with a more sophisticated name. I'm not sure about why it was so successful in Vietnam, but I do know that Guerrilla warfare is very effective when executed properly, because there are very few casualties and a lot of damage is done to the enemy. It also works really well when the people using guerrilla warfare know the terrain well, because they would have an advantage over the enemy.
Hope this helps!
Florence was the most famous. :)
The Open Door Policy is a term in foreign affairs initially used to refer to the United States policy established in the late 19th century and the early 20th century, as enunciated in Secretary of State John Hay's Open Door Note, dated September 6, 1899 and dispatched to the major European powers.[1] The policy proposed to keep China open to trade with all countries on an equal basis, keeping any one power from total control of the country, and calling upon all powers, within their spheres
