Was Sweden's Vasa built from the oak of the enemy?
A new tree ring study of Sweden's Vasa warship hopes to prove that it was partly constructed out of oak from Poland, the enemy the Vasa was built to fight.
"The purpose of Vasa was to fight the war against Poland, however business is business," points out Fred Hocker, research director at the Vasa Museum.
"If you were selling timber to the enemy, in the short term it's to your advantage to sell raw material for a project you anticipate will take longer than the war might take."
The Poles' bet paid off: the dangerously unstable and top-heavy Vasa sank only minutes into her maiden voyage.
It then lay for 333 years at the bottom of Stockholm's harbour before it was salvaged in 1961.
Hocker is now working with Aiofe Daly, an expert in using tree rings to find out when and where timber was felled, to locate the origin of all of the important pieces of wood from which Vasa is constructed.
Daly's first exploratory study found that some of the long straight planks came from western Sweden or Norway.
Hocker says that both this and the Polish timber would have been bought from Dutch timber merchants working at the international timber market in Amsterdam.
Daly will return next month to carry out a more thorough investigation.