Vietnam is a country with an unusual record of beating off larger invaders - China, France, and the United States; they even repelled a couple of invasion attempts by Mongolia in her prime (much of this ass-kicking can be attributed to their diligent study of The Art of War). Vietnam has been involved in wars from about 1945BCE to 1979CE, although like any small country with important resources (rice, water buffalo, spices, pot-bellied pigs, urm... more rice), it has been through numerous conflicts to retain sovereignty throughout its existence. Despite all the destruction this entails, Vietnam still has enough forest to spring surprises, as when several new large animal species were discovered there in the 1990s.
Of course, Vietnam didn't always play the "little guy beating up big guy" role, as they consistently slapped around the kingdom of Champa for a couple hundred years, eventually extinguishing it in 1832.
These days, Vietnam hasn't been beating up many foreign invaders militarily, but it does have the second fastest growing economy in the world, joining the World Trade Organization (WTO) in January 2007, and thus is beating up foreigners economically. Ironically, this just means that foreign invaders are now welcomed in the form of land developers, many of whom are currently chopping up the landscape to make room for pretty hotels and resorts.
 War! Hunh! Good God y'all, what is it good for? Absolutely nothin'!
Even now, the name Vietnam is enough to start arguments in America over whether the USA should have got involved, or what tactics should have been used. In fact, the specter of the Vietnam War hangs over the decisions which led to the Iraq War.
 Politics makes strange bedfellows
In 1995 the US and Vietnam began to kiss and make up. Since then the two nations have had closer ties. The reason is because China has claimed the entirety of the South China Sea as its territorial waters. The Chinese make this claim despite the fact that that the sea borders Vietnam, the Philippines, Malaysia, Cambodia, Indonesia, and Singapore. Furthermore, China and Vietnam have had bad blood going back thousands of years. The result is that these countries are looking for some American muscle to deal with the Chinese just in case. Meanwhile the US had been building economic ties with Vietnam and is looking for more allies in the region for leverage against China. In 2009 the US Navy was invited back to Da Nang (the captain of one of the ships having been a Vietnamese refugee as a young child) indicating both nations might be more than happy to bury the hatchet.