Afghanistan US United states
(Image: AP/David Goldman)

At the start of May, the United States began the final withdrawal of its armed forces from Afghanistan. Scheduled for completion by the 20th anniversary of the 9/11 attacks, this retreat will end the longest war in American history.

Overlapping with the parallel conflict in Iraq as part of George W Bush's "War on Terror", these twin invasions inflicted hundreds of thousands of casualties, mostly civilian. Millions more were displaced. The cost to US taxpayers was $6.5 trillion. That's enough to buy every American household a sports car. Few would argue it was money well spent.

However even before the last boots have left the ground, warmongers are beating their drums again. Some have set their sights on Iran. Others spy a bigger fish in China. North Korea is another perennial bogeyman. In the minds of these armchair warriors, America must always have an enemy.