The investment of the siege of Mafeking began in mid-October, 1899 at the beginning of the Second Anglo-Boer War. The British military authority, by the order of Colonel R.S.S. Baden-Powell, commander of the Frontier Forces, took over control of the civil Post Office operation in Mafeking.
Baden-Powell's plan for the defense of the town called for the positioning of armed defenders - regular British soldiers, British South Africa Police (black Africans), and local townsmen - at fortified defensive positions, or forts, that ringed the town. To keep the morale of the defenders high during the potentially long run of the siege, Baden-Powell believed that their ability to stay in regular contact with friends and loved ones in town was of tantamount importance, and that the only way to insure uninterrupted movement of the mails was to place Post Office operations in the hands of the military.
The military authority bought up the entire stock of postage stamps in the Mafeking Post Office and then had the stamps overprinted "Mafeking Besieged" and surcharged for the special rates of the siege mail by the local printer, Messrs. Townshend & Sons. When the supply of overprinted/surcharged stamps was exhausted in early 1900, the famous photographic or "blueprint" stamps, bearing the portraits of Cadet Sgt. Major Warner Goodyear of the Cadet Bicycle Post and Colonel Baden-Powell, were produced.
At the time of the siege, there were three active canceling devices in Mafeking;
"MAFEKING C.G.H." squared circle date stamp (Goldblatt SC 6), which had been in use since November 1895, when British Bechuanaland, in which Mafeking was then located, was annexed by the Cape of Good Hope.
Mafeking Siege Cancel
"MAFEKING C.G.H." 25mm single circle date stamp (Goldblatt CDS 25), which would become known as the "Mafeking siege" cancel.
Single circle "squared dot" 21mm date stamp (Goldblatt CDS 16, Holmes Type 2), which was also extensively used as the date stamp on telegrams received in Mafeking. This cancel became known as the "Mafeking telegraph" cancel.
Two other cancels were known for Mafeking. The barred oval numeral cancel (BONC) no. 638, which was used from the opening of the Post Office in Mafeking in 1885 until annexation in 1895 may still have been present in an inactive status. A second BONC, no. 1045, which had been produced as a standby canceler for British Bechuanaland but was never postally used, was also present.
For reasons that were never recorded by either the military authorities or the civil Postmaster in Mafeking, Mr. J.V. Howat, who continued to function in his position during the siege, the 25mm "Mafeking Siege" was used to cancel all siege mail.
According to van der Walt (1986), this cancel was introduced in Mafeking sometime after the annexation, but it is not known exactly when. The earliest reported usage of this cancel is April 15, 1897. Compared to the frequently used squared circle date stamp, the "Mafeking siege" cancel has been infrequently reported out of Mafeking, particularly after the relief of the siege. The latest reported use is January 27, 1906 as a receiver on a Christmas post card sent by Baden-Powell from Battersea, S.W, UK to Major Francis William Panzera, stationed in Francistown.