I especially enjoyed reading chapter six of Age of Empire. I thought it was a good representation of the imperialist attitudes that many nations had in the period between (and especially after) 1875-1914. In chapter six, Hobsbawm highlights some key features of nationalism; they are, "flag waving", patriotism (nation- or race-identification), a national language, and a national education.
It seems to me that Hobsbawm's logic is that patriotism is a result of a nurtured education where the nation is taught as something to be held in high esteem; Hobsbawm gives the example of the United States, where he (correctly in my opinion) says that the flag was worshiped and pledged-to every day in schoolhouses across the country. A national-universal language only helps this process to patriotism because if everyone speaks alike, everyone is alike (so the logic goes). We can see language barriers in today's world in nations like India, Switzerland, and Belgium, but also in our own country where people in different regions of the country have different accents (in Texas they are Texans first, American's second).
Democracy and political involvement are also key components in the nationalism equation. If the once-alienated classes have the right to vote (i.e. were recently granted suffrage), then they are more likely to be politically active within the nation's political process instead of working around it through revolution. Thus, the once politically isolated will become a part of the true nation, and they will begin to call themselves part of the nation, which leads to patriotism. Patriotism leads to nationalism, nationalism leads to imperialism, and imperialism leads to World War One (see esp. graphics on pages 350 & 351).
"Nationalism... attacks democracy, demolishes anti-clericalism, fights socialism and undermines pacifism, humanitarianism and internationalism. ...It declares the programme of liberalism finished (Alfred Rocco, 1914). I think Hobsbawm uses this quote to show that nationalism treads over democracy (fair government by the people), is all-powerful, ends welfare-state-mentality, and easily shrugs-off pacifism and constraint. Again, I would say that Hobsbawm's chapter six is perhaps the most important chapter thus far, because it is a very important connection to The Age of Empire, and even our world today.
Immanuel Kant, in his [Towards a] Perpetual Peace, writes, "the civil constitution of every state should be republican." In the Age of Empire, most of the countries Hobsbawm looks at were republican or were in the process of becoming more republican. What, then, was the cause of the lack of peace between countries, as it was not lack of republicanism?