Original: In South Africa during the Second Boer War, Baden-Powell was besieged in the small town of Mafeking by a much larger Boer army (the Siege of Mafeking).
Simplified: It was formed during a siege in the Second Boer War. During the Second Boer War, Baden-Powell was besieged in the small town of Mafeking by a much larger Boer army (the Siege of Mafeking).