The war of 1812 is often called the Second War of Independence, for Britain attacked and almost defeated the US (see burning of the White House) in an epic battle. However, it was not exactly a second war of independence, for the US was the one that initiated the conflict by invading Canada, then a colony of Britain. To gain wide-spread support, the US made it so that it sounded like the UK was the aggressor.
The answer is the North Vietnamese took over the South Vietnam spreading communism Southward and this proved the domino theory (if one country come under the influence of communism, the surrounding countries would follow).
