Disunited Kingdom

   Britain has had its fair share of foreign policy fiascoes over the past century: the disastrous decision to seize the Suez Canal from Egypt in 1956, the appeasement of Hitler in the 1930s, and the military strategy in World War I, which destroyed a generation and gave us such synonyms for military misadventure as Gallipoli and the Somme.
   "Brexit," the British vote Thursday to leave the European Union, will surely join this list of disasters. The EU is the latest of a series of multinational organizations set up after World War II to ensure that there would never again be a pan-European war and to create the conditions for a new European prosperity after the destruction wrought by the war against the Nazis. The EU has admirably succeeded at both.
   British voters were deeply split on whether to stay in the EU but in the end voted 52% to 48% to get out. Just one indicator of the damage Brexit will cause: Consider that the pound has already been pummeled, the British stock market is reeling and global markets have been rocked, including the Dow. Every serious economist has predicted that Britain will incur significant losses as a result of leaving the EU, including the Organisation for Economic Co-operation and Development, which estimated that British economic growth would be 5% smaller by 2030. But the consequences go far beyond just economic ones.
   Because Scotland and Northern Ireland want to remain part of the EU there is the quite real possibility that Scotland and even Northern Ireland might now choose to go their own way on membership within the EU and the "United Kingdom" would suddenly effectively be only England and Wales.
   The vote has also deeply divided the ruling Conservative Party. British Prime Minister David Cameron, who blithely promised a vote in 2013 on EU membership, seeming to think that it would be a foregone conclusion to stay, has rightly said he will resign. Many of the key leaders of Cameron's Conservative Party were on opposite sides of the "Remain" or "Leave" question.
   In the wings possibly to succeed Cameron is the flamboyant and opportunistic former mayor of London, Boris Johnson, whose cult of personality and nationalist views suggest a smarter version of Donald Trump. Trump is himself crowing that Brexit is happening as it serves to reinforce his own anti-immigration stance, which was a central plank of the Leave campaigners in Britain.
   The vote has also empowered the British National Party and the UK Independence Party, which are ultra-nationalist parties sustained by a growing suspicion and hatred of immigrants.
   And it will also empower other European ultra-nationalists, such as the French National Front party, which is already demanding that France have a vote to leave the EU.
   It's not often that one decision can cripple your own economy, damage global investor confidence, imperil one of the most successful alliances in modern history, foster the rise of ultra-nationalists, precipitate the possible breakup of your own country, deeply divide your own party and cause a great schism between voters of every ideological stripe, but this is one of them.

Well done, David Cameron.

    Peter Bergen is CNN's national security analyst. He grew up in the United Kingdom and studied modern history at Oxford. The opinions expressed in this commentary are his.