You're talking about the Sika dwa, the golden stool of the Asantehene or King of Asante; the war in question, sometimes called Yaa Asantewaa's war, was actually a rebellion against British occupation of the Asante state (Asanteman) triggered by a very specific disrespect of that stool. The basic situation was this: As pointed out elsewhere, the mythology of the Sika dwa does have it descending from the heavens to the first of the Asantehenes, Osei Tutu I in 1698 or so, when he was still Kumasehene or king of Kumase. In building the Asante Confederacy, Osei Tutu needed a symbol that would elevate Kumase above other Akan city-states, particularly Denkyira, that had proven difficult rivals. The stool provided that, because Akan cultures carried a common belief that a family stool was a place of rest for the soul as well as the body. As the greatest of the family, the stool was most vital of the possible symbols of spiritual and temporal rulership, and meant this for the whole nation. It is a wood stool that is ornately decorated with precious materials and particularly gold.

The issue of the war turned on its symbol of rulership. In 1896, faced with a British military column, the Asantehene Agyeman Prempe I elected to capitulate and be deported rather than bring the Maxim guns down against his people. The "war" was rather contrived, and really designed to force the issue of British overlordship, and they got their wish. In 1900, the Governor of the Gold Coast (Sir Frederick Hodgson) decided to further establish British supremacy by taking protectorate one step further when announcing formal annexation: he demanded the remaining Asante royals produce the Sika dwa so that he, the Governor, could sit upon it. Well, besides not being Asantehene, Hodgson didn't understand that nobody was ever actually permitted to sit on the stool--kings were lowered over it and raised back up, when installed--so his demand was an act of profound disrespect to the very spirit of Asante. While elders were deliberating what to do about this incredible outrage, the Queen Mother of Ejisu, Yaa Asantewaa, took initiative to rally people to the banner of war to eject the British from Asanteman. If not for four Maxim guns and some defenders from nothern Nigeria, the strongpoint in Kumase might well have been overrun. In the meantime, the Asante royals still in Kumase buried the Golden Stool in an unknown location. Although British relief columns put down the rising and completed the annexation of Asanteman to the Gold Coast colony, they did not find the stool.

The Sika dwa however still threatened to cause another rising two decades later. From its hiding place, it was unearthed by some non-Akan workers building a road in 1921 found the stool's burial site and pried off some of the ornaments before someone else discovered their find and it became known to the remaining Asante family heads and leadership in the country. They demanded, unwaveringly, that the British must return the stool and hand over the looters for trial and punishment by Asante law. By this time, the British had seen so much difficulty in trying to impose themselves on Asanteman that conciliatory measures were far preferable and might actually begin to salvage feelings between the two groups. Note that the Asantehene Prempe I was still in exile in Sri Lanka the Seychelles at this point, as he'd been for 25 years (he wrote many appeals to the British for return based on history, which were published in book form some years ago ), with many of his family. To wave off the Sika dwa again would be inviting a further rising, beyond simply being bad PR. So the British decided to let the Asante courts in Kumase try the road workers; the court sentenced them to death, which the British commuted to exile, in an agreed-upon solution. The British colonial government paid to have the stool restored and returned to Kumase the next year, which paved the way for the return of Prempe from exile in 1924 and his resumption of the throne. So the story of the Golden Stool in Asante-British relations does not end with the war in 1900! The stool is still in existence today, though it is rarely seen unless a new King is being installed. Although the function is now more ceremonial, it is still a fundamental part of Asante identity and pride.

(For more on the war and Asante society, see Natasha Gray, "Yaa Asantewaa and the Asante-British War of 1900-1," International Journal of African Historical Studies 38, no. 2 (2005): 383-407.)