The German Marshall Fund of the United States annually does a survey on important "transatlantic trends", which can make an interesting read. One of the questions asked is: "Please tell me to what extent do you agree with the following: Under some conditions, was is necessary to obtain justice." (Q29.2). The answers are quite revealing (see graphic below).
Is it a surprise that in the USA and Britain more than 50% agree with this statement (USA in 2009: 37% "strongly agree" and 34% "agree somewhat"; Britain in 2009: 20% "strongly agree" and 35% "agree somewhat")? It is interesting that in these two countries, who are most responsible for the wars in Iraq and Afghanistan, a high proportion of the population agrees that war is sometimes necessary - higher than in Turkey, a country which a very visible tradition of militarism. Most of the European countries trail far behind - 18% in France, 19% in Germany, 16% in Italy, 29% in the Netherlands, 19% in Poland, etc.
The good news however is that in most countries the figures have consistently gone down - including in the USA and Britain, but even more so in France, Germany, Italy, or Poland.
Source: Transatlantic Trends: Topline data 2009, http://www.gmfus.org/trends/doc/2009_English_Top.pdf