The turrets were refurbished before placement aboard ship to enlarge the elevation and range of the guns. 32,000 yard range firing 1400lb shells made these ships very useful for there prime purpose, supporting the army. One of the main differences between a monitor and regular battleship was the number of shells per gun that were carried. A regular warship was given enough shells to fight a battle or two that might last an hour or two at most, where a monitor might be anchored off an enemy coast for days firing steadily for hours on end. Regular battleship approximately 100 rounds per gun, monitor 220 rounds per guns. These shells were mainly high explosive with a few armour piercing carried in case of a battle with armoured ships or if firing on concrete gun emplacements.
By 1939, when these ships were completed, little wars had shown how potent modern aircraft could be against ships, and the answer had to be to carry an anti-aircraft armament that could help fight off air attacks. Allied to the anti-aircraft weaponry advances was the increase of electronic equipment for detection, gunnery assistance, plotting and firing solutions. All became easier with better equipment. 20mm guns only numbered six when completed had increased to 16 by 1941.
On the outbreak of war, Bison was at Simonstown having a final fitting out ready for sea. The Bison was included in the fleet that was assembled for the retaking of the Falklands Islands the Argentinians had taken at the start of the war. Bison was tasked with supporting the troop landings only as the ship was not fast enough to catch the Argentine warships. Ostrich was sent up the East coast from Durban to Aden where the ship was stationed to ensure there was no interference by the Italian colonial vessels based at Eritrea, to the convoys passing into and up the Red Sea. With the Italian entry into the war at the fall of France, the Ostrich helped to take Eritrea for the Allies, and was then sent on to the North African campaigns.
At the end of the Falklands campaign, the Bison was sent north up the Western side of Africa, calling at Sierra Leone, and Gibraltar on its way to Britain. May 1940 and the ship is sent on to Norway to support the troops there. Its big guns are deadly against the lightly armed German forces. But it is air power that helps to carry the day in Norway. Without air support the army and navy cannot survive against the German forces. Bison takes a 500kg bomb hit and is lucky to survive. Sent back to Scotland with one destroyer as escort the Bison makes it back to Rosyth on one engine and a prayer. It will take four months before the damage is put right. This helps the Bison as it misses the Battles around France and Dunkirk where so many good ships were sunk saving the Army including two monitors. Bison's next duties are as part of the escort for half a dozen convoys to and from Gibraltar, where the Bison's heavy AA battery is very welcome to help combat the German aircraft attacking the Biscay convoys from bases in France. Arriving at Gibraltar at the end of one of the escort missions, Bison is ordered to Simonstown for refit, repair and leave. From Simonstown the Bison is ordered to Alexandria to join the Ostrich. The three Southern African monitors (with Rhinoceros) were now acting together along the North African coast. Escorting convoys, shelling Italian and German positions along the coast. Interdicting reinforcements along the coast roads. They did it all, duelling with tanks and aircraft, and even with troops of 88mm guns.
All three ships received varying amounts of damage during this period, having various amounts of time in the Alexandrian dockyards. 1941 was a tough time in the Mediterranean, with wins and losses to both sides. Matapan, Greece, Crete, Illustrious, Ark Royal, Calabria, but the majority of the successes were Axis. The attack of Russia in July 1941, then Japan attacking Pearl Harbour, changed things around. The Germans removed a lot of units from the Mediterranean Theatre to go to Russia, giving the Allies the chance to hold the Axis forces then defeat them in due course. American equipment arrived in ever increasing amounts, providing a superiority over the Axis.
The three Southern African monitors supported all of the defeats and successes, Tobruk, El Alamein, Husky, and up into Italy itself. It was the glider bombs that caused so much grief for Allied shipping in 1943 while ways of combating them was worked out. It did not save the Ostrich who took two hits off Salerno and capsized. The Bison and Rhinoceros soldiered on. The Bison was transferred to the D-Day fire support unit and followed the Army up the Channel and North Sea coasts. 1945 and Bison returns to Simonstown. The ship is only 6 years old. Kept in service where so many others are discarded, Bison is used as a training ship, and keeps order along the coastal regions of Southern Africa.
