When British forces pull down the union jack for the last time in Afghanistan this year, it will be a hugely symbolic moment. It is not just that the departure marks the end of 13 years of British involvement in combat in that troubled country. The surprise is that it could also signal the end of a century or more of unbroken warfare by British forces.

Next year may be the first since at least 1914 that British soldiers, sailors and air crews will not be engaged in fighting somewhere – the first time Britain is totally at peace with the rest of the world.

Since Britain's declaration of war against Germany in August 1914, not a year has passed without its forces being involved in conflict. It is a statistic that has been largely overlooked, and not one about which the government is likely to boast.

The past 100 years have seen two world wars, large-scale conflicts in Korea and Iraq, and small-scale actions in Africa, the Middle East and Asia. There have been punitive operations in defence of empire, cold war operations, post-9/11 support for the US, and the Troubles in Ireland....