(All Souls Entrance Exam General Paper 1 Q 1)
The libertarians won the twentieth century. Libertarianism is generally viewed as right-wing because they support free-market capitalism and currently people care about the economy more than anything else. However, on their social policy they lean more left-wing taking the view: "There is no place for the state in the bedrooms of the nation" (Pierre Trudeau). Furthermore their stance on the use of force (eg. military conflict) is to use it only in self-defence. These three positions have been the winning sides in during the twentieth century.
First free-market capitalism. The first major assault on free market capitalism in the twentieth century was prohibition in the USA. It was a complete and utter failure with illegal alcohol widely produced and vast amounts of smuggling across both the US-Canada and US-Mexico borders. Next would be the only real loss free-market capitalism would suffer during the century - the introduction of social safety nets during/after the Great Depression. Many countries saw the introduction of various social safety nets (socialize medicine, social security, unemployment benefits etc..) after the suffering they experienced during the Great Depression. This was only a small victory for the left since this enabled free-market capitalism to survive despite a continuous cycle of boom and bust by preventing the severe economic devastation which can lead to radical political change. However, arguably the biggest economic change of the twentieth century is globalization. Globalization was started by western countries freely opening up their capital and commercial markets using a combination of deregulation and free-trade agreements; the greatest example being the creation of the European single-market via the EU. This model was then forcibly extended to developing nations by the IMF and World Bank. Globalization of free-market capitalism has fundamentally changed the relationships between nations and between nations and industry as evidenced by the fact that Walmart would be the 25th largest country by GDP. Thus globalization has been a massive victory for the libertarians.
The second arena where libertarianism has won out is social policy. At the beginning of this century women were considered property and homosexuality was punishable by death in most countries. While blacks weren't slaves anymore they were frequently segregated from whites and excluded from positions of power. By the end of the twentieth century women enjoyed the same rights and privileges as men in most countries as did blacks and in the two years following the first homosexual-marriages would be performed. The middle of the century saw constraints on sexuality and drug-use begin to lift with legalization of marijuana gaining popular support at the end of the century. The only misstep during the twentieth century on this front was the rise of eugenics which inspired forced-sterlization programs in several countries and the Nazi exterminations. Fortunately the Nazi's were defeated in WWII and sterlization programs were publicly condemned and repealed by the end of the century.
Finally the last aspect to consider international affairs. The twentieth century saw the crumbling and collapse of colonization and European Empires. The first world war was primarily about colonization, and although Germany came out the worse everyone involved lost more than they gained. After the swiftly following second world war the colonial powers no longer had the means to keep hold of their colonies and many returned to independence, another win for the libertarians. Next came the Cold War which epitomized the conflict between free-market capitalism and authoritarian socialism, with free-marketism coming out the victor followed by the disintegration of the USSR and its conversion to capitalism. Furthermore, libertarianism believes only in using force for self-defence and a quick skim of the conflicts will reveal the defenders were typically victorious - WWI (Germany & Austria threw the first punches), WWII (Hitler & Japan were the aggressors with Britain and the USA the defenders), Falkland Islands War (Argentina the aggressor, Britain the defender), etc... with the exception of wars of independence. Finally the combination of nuclear weapons and globalization reduced the tendency for warfare since the consequences for both sides would be severe reducing the amount of global military conflict. Most current conflicts are essentially civil wars between a large minority group and the ruling majority - a situation where both sides feel they are acting in self defence.
Thus, it is libertarianism which won the twentieth century which we now see in the public opposition to surveillance, the rise of media piracy, the ideology of open-science and embrace of human rights by the legal system.