What should happen to treasures stolen in war? In the modern era, we believe, of course, that they should be returned. But what about treasures stolen over 300 years ago, that have since found a new home? That's one of the questions Colin Woodard explores in the summer issue of Military History Quarterly, using as a starting example the so-called Silver Bible taken by the Swedes in the Thirty Years War. "Over the past two decades, globalization, changing attitudes, and the spread of both international law and civil lawsuits have emboldened aggrieved nations to demand the return of cultural property seized by enemy forces decades or even centuries ago, and a few holders of these spoils have complied," he writes. That's not true in all cases, though.

"Returning plunder to its rightful owner" is more complicated than it seems, particularly when there's disagreement about the "rightful" owner. "After all," explains Woodard, this concept has changed over time: "for much of human history, armies plundered the vanquished as a matter of course and sometimes went to war solely to do so." So back to that example:

Determining the legitimate owner of something as old as the Silver Bible can be a futile task. The Ostrogoths who created it died out centuries ago, and the Czechs weren't in control of Prague when the Swedes arrived in 1648, the city being part of the now extinct Holy Roman Empire. Sure, the bible belonged to German-speaking emperors for 60 years, but nobody knows how they extracted it from the Benedictines. The Swedes have at this point possessed the book six times longer than anyone in Prague ever did, so it is not surprising that they don't feel compelled to hand it over.

The fact is, there is no legal or customary basis to demand the return of anything plundered prior to the turn of the 20th century. Doing so successfully is ultimately a matter of public relations, of convincing whoever possesses the object that giving it back is the right thing to do.
And that's only one of the cases Woodard discusses. Looting and deliberate cultural destruction in the 20th century gets, if anything, even more complicated. Have a look at the full article.