Hostage is one of those words that can cause confusion to people new to historical fiction set in the early Middle Ages. After capturing the Saxon fortress of Eresburg and destroying the Irminsul in 772, Charlemagne took 12 hostages, an event recounted in my second novel, The Ashes of Heaven’s Pillar.

Today we think of a hostage as someone held against their will to extort money or some other demand, but the word’s meaning was slightly different for Charles and his contemporaries. To them, hostages were a means of making sure an enemy kept a commitment they made.

The vanquished took an oath of loyalty to the Frankish king, but swearing to a saint was not enough to reassure the monarch – or anyone else with sense. The vanquished party also surrendered hostages, often the young sons of important men.

As long as the vanquished behaved themselves and kept their oaths, the hostages would be treated as the king’s guests. If the vanquished broke their promises, the king could do whatever he wanted to the boys, whether that was sending them off to a monastery to be unwillingly tonsured, selling them into slavery, or killing them.

So with the lives of their offspring at stake, one would think the vanquished foes would be motivated to keep their promises. But hostage-taking often didn’t work in practice. When Charles was otherwise occupied – for example a war with his ex-father-in-law in Lombardy in 773 – the Saxons would move to retake lost territory. To the Franks, they were breaking a sacred oath. The Saxons, who never wrote down their story, might argue an oath at the point of a sword was invalid.

A sad part of the history remains untold – what happened to the hostages.