Realpolitik is an approach to politics, diplomacy, and foreign relations that strives to be non-ideological, as in doing what is best for the national interest without getting hung up on unjustified diplomatic habits or popular sentiment. An example of Realpolitik would be the United States reaching out to China in the 1970s, despite protest that America should not associate with communists. Both countries gained great economic benefit from the better relations, but certain people think it never should have happened.
The term Realpolitik comes from Ludwig Son von Rochau, a German writer and politician in the 19th century, who used it to refer to the diplomatic approach of Klemens von Metternich, German-Austrian politician and statesman who is considered the foremost diplomat of his time. Metternich was the architect of the Congress of Vienna, an important diplomatic meeting in 1814-1815 which settled many outstanding issues stemming from the French Revolutionary Wars, Napoleonic Wars, and the dissolution of the Holy Roman Empire. The Congress of Vienna, which was held after 25 years of continuous war, mostly with Napoleon, ended up serving as the framework for European international politics until 1914, when World War I broke out.
To its detractors, Realpolitik is sometimes seen as Machiavellian, based on “the ends justify the means,” coercive, and amoral. To its proponents, Realpolitik is simply acknowledging reality and doing the best one can in international politics in light of obvious realities. Practicing Realpolitik can be politically difficult, and may mean defying the popular opinion. However, it contrasts with the notion of a ruler or diplomat who acts exclusively in accordance with popular whim, with little direction of his own.
In modern times, the foremost practitioner, advocate, and popularizer of Realpolitik is Henry Kissinger, who was Secretary of State under the American presidents Richard Nixon and Gerald Ford, between 1973 and 1977, and was the dominant force in American foreign policy for most of the 1970s. Kissinger was a highly controversial Secretary of State, mostly for his involvement in the Vietnam War. His critics attack him for extending the Vietnam War into Laos and Cambodia, while his supporters point out that North Vietnam had always ignored borders between all three countries, so for the United States to pretend that resupply stations were not in Cambodia or Laos would be suicidal. For the time being, it does not seem that history has come down conclusively on either side, but for better or for worse, Kissinger’s actions during the Vietnam area are a standard example of Realpolitik.