To what extent does the War on Terrorism represent a break with previous United States foreign and defense policy?
The War on Terror is a very abstract war - it is a war against an idea and a decentralized group, or groups, of terrorists spread throughout the globe. This is very different from the Cold War, which, while still a war against an idea - communism - was a very clear cut war against the Eastern Bloc and the Soviet Union. It was very clear who our "enemies" were, and the country was relatively united in what to do about it in terms of military action.
With the War on Terror, we are fighting al-Qaeda (in more than one country), the Taliban, local Islamic militants in several countries, and even homegrown terrorists in the United States. A war strictly against terrorism, as has been admitted by US Generals, has no military solution. It is much more a war for the economy, and for hearts and minds over the long term.
Perhaps the view expressed in the previous post that war on terror is a very abstract war, is the major cause of confused state of the USA approach towards fighting terrorism. The Afghanistan war was definitely an action against terrorism and there was nothing abstract about it. It was a very strong, quick and decisive action taken by the USA. But then on many issues the USA is content to pay just lip service against terrorism. On one side, it turns a blind eye towards terrorist activities of some governments, and even provides them with aid that is diverted to terrorist activities, on the other side it and takes excessive precautions to prevent some highly unlikely and undefined terrorist acts. For example there was a recent newspaper report of a six year old girl, a US citizen being denied an airlines ticket because her name appeared on list of persons suspected to have terrorist links. Parents of this girl were, however given tickets without any problem.
I think this combination of quick and strong action on one side, and meaningless ineffective action on the the other, have been characteristic of the US approach towards terrorism for quite some time.