Why was there so much conflict in the Balkans in the 1900s?
The conflicts in the Balkans during the 20. century are a complicated issue: emerging nations, the fall of the Ottoman Empire around at the same time as the Austria-Hungary Empire, and the enormous interest bigger powers have shown in this region, and are still showing today. A very good book on the issue is "Black lamb grey falcon' by Rebecca West.
What did Winston churchill mean when never in the field of human conflict was so much owned by soo many to few?
Any diamond is valued today by its cut, clarity, carat weight and colour. In the 1900s, grading diamonds was not so sophisticated. Larger stones had value, simply because of their carat weight. Coloured stones were not so prized as they are today. In order to answer your question, you'd need particulars about the stone you were trying to value.