Ok this is a bit long but plausible so please bare with me. The war could start off with Scotland agreeing to stay with the UK if they help them set off a dirty bomb in France. Tensions with France and the UK (mainly England) are still around today just dulled down. The dirty bomb would be in effect of the fisheries. Basically Britain joined the EEC (modern EU) in 1973. This is when the fisheries started getting depleted (included in the image). Now the tension to start this off could be something simple as a Uk leaving the EU at the next election 2015 due to the upcoming politician Nigel Farage leading UKIP causes a landslide victory. Also possible because lib dems are going no where, Labour no one trusts Ed Miliband and Conservatives people are getting fed up of the plain lies. After the UK leaves the EU french ships still harass and fish well inside the borders. So local fishermen take up arms saying they will fight to the death to try to stop the ships. When accidentally a french ship attacks an unarmed small boat filled with say 40 young children killing all. National outrage, drops dirty bomb declares war.
@TheSmiler why would Scotland government use terrorist tactics to ease economic problems? I don't see a realistic reason for any of the Big Three (Britain-France-Germany) to wage an open war at each other at the present moment. Problems do exist on the fringe of EU societies that may call for concentrated military operations, from Cyprus to Basque to Kosovo to Crimea, but if you place them on a map you'll see that they are literary on the fringe. There is however another kind of fringe which could realistically cause unrest, tensions, continent-wide escalation of violence and may be a reason for, say, German troops to come to London: and that is civil unrest. Economic tensions in the contemporary world, after a century and more of being funneled and (mis)directed into nationalisms, are finally getting back to where they belong, and that is, to use a marxist term, class struggle. That, and the fact direct democracy emerges in last years as a truly obtainable and functioning type of "government". The gap between the "people" (the voters) and the rulling oligarchies of the representative democracies, fueled by the very real threat of the BigBadCorporation - it's becoming more and more of a problem. Sure, nationalisms and petty local (local=nation wide) concentrations of power may still pose threat to human lives - even more so then ever! - but if you want realistic reasons for a continent-wide war, I'd say investigate the sources of contemporary problems, not just stick to history books that just want to see "history repeating"...
I would rely on economic imbalance within the EU and a future collapse of the Euro currency. The failing economies (Spain, Portugal, Italy, Greece) refuses a reform package proposed by Germany in order to prevent a currency collapse that would spread the depression to more prosperous countries. So on one side you have Germany, Netherlands, Scandinavia, and the Baltic States. On the other, you have Spain, Portugal, Greece, Cyprus, and most importantly Italy. France and Britain try to stay neutral but France is pulled in on the Italian side and Britain on the German side. Research two people: Belle Grillo of Italy and Alexis Tsipras of Greece. Then picture those two gaining power, banding together, refusing to comply with German policy, and daring the rest of the continent to force their hand.
It does not have to be the two countries 'most likely' to go to war. It should be the two countries that you think fit. Logic does play a role in writing, but not everything has to be 100% valid.
As I said it depends if an incident were to happen and the wrong politician was in power it could sway a decision. Regarding the OP you could see about doing something that the Call Of Duty MW2 No Russian mission (violent). If North Korea caused the ferry capsizing in South Korea I could easily bet money on that leading to serious violence. Most countries are one tip from the edge; at the moment they won't do it as it hasn't really happened however it isn't that far away
I haven't seen too much discussion about the European elections on this forum, but this thread seems like an appropriate place to mention them. This is how it goes: 1. The fundamental flaw of capitalism (it requires never-ending growth, which a child could see is impossible) is exposed, and several nations sink further and further into debt, causing extensive economic problems throughout Europe. 2. Faced with increasing hardship, unemployment, and so on, people are unable to see the real root of the problem (see 1) and instead opt to blame immigrants and the EU, leading to a rise in extremism throughout the continent. 3. Bang! Seriously, I wish it were a bit less plausible...
