Of the three candidates aspiring to be prime minister, NS readers will be aware that I believe Brown is the best - well, um, er, the best of a mediocre bunch.

But on Afghanistan he is wrong. Plain wrong. He is the one who needs to "get real". In the first debate, Cameron seemed to imply that Britain might go to war with China. In this second debate, Brown seemed to imply that he'd be willing to go to war with around 100 nations on earth.

Don't believe me? Here's the killer quote from the PM:

We've got be to be clear: we cannot allow terrorists to have territory in the world that then they use as a base for attacking the United Kingdom.

According to the Council on Foreign Relations, "Al Qaeda has autonomous underground cells in some 100 countries". So how does Brown plan to deny them their "territory", their "base", in each? God help us all if Afghanistan is the template.

This is a serious point. The idea of engaging in foreign wars to deny al Qaeda safe havens or bases is as impractical as it is pointless. Again, don't take my word for it. Check out this analysis from pro-war policy wonk Stephen Biddle (who has been a civilian adviser to General Stanley McChrystal, the US commander in Afghanistan):

The Taliban movement in Afghanistan is clearly linked with al-Qaeda and sympathetic to it, but there is little evidence of al-Qaeda infrastructure within Afghanistan today that could directly threaten the US homeland. If the current Afghan government collapsed and were replaced with a neo-Taliban regime, or if the Taliban were able to secure political control over some major contiguous fraction of Afghan territory, then perhaps al-Qaeda could re-establish a real haven there.

But the risk that al-Qaeda might succeed in doing this isn't much different [from] the same happening in a wide range of weak states throughout the world, from Yemen to Somalia to Djibouti to Eritrea to Sudan to the Philippines to Uzbekistan, or even parts of Latin America or southern Africa. And of course Iraq and Pakistan could soon host regimes willing to put the state's resources behind al-Qaeda if their current leaderships collapse under pressure.

Many of these countries, especially Iraq and Pakistan, could offer al-Qaeda better havens than Afghanistan ever did...We clearly cannot afford to wage protracted warfare with multiple brigades of American ground forces simply to deny al-Qaeda access to every possible safe haven. We would run out of brigades long before Bin Laden ran out of prospective sanctuaries.

Oh, and one final (key) point. Do you know how many members of al Qaeda are believed to be in Afghanistan right now? Does Gordon Brown? "The maximum estimate is less than 100 operating in the country. No bases. No ability to launch attacks on either us or our allies." That's the verdict of President Obama's national security adviser, General James Jones.