The greater part of the British Home Fleet was now at sea hunting for the the German battleship Bismarck. The strategy was to make an informed guess on her likely passage and then keep ships with a good lookout on the route. But the Royal Navy had one technological innovation to assist.
For a good analysis of the battle see the 2019 book British Cruiser Warfare: The Lessons of the Early War 1939–1941.
23 May 1941
In the AM, atmospheric conditions in the Denmark Strait were unusual in that visibility was clear over and close to the ice field. Suffolk took advantage of these conditions, patrolling along a line more to the east across the top of the minefield than would normally have been safe, and to be close to the edge of the mist, in order to be able to take cover quickly if the Bismarck appeared. Norfolk was stationed about 15 miles abeam of Suffolk.
At 1922, while on a southerly course, Suffolk sighted Bismarck and Prinz Eugen seven miles off her starboard quarter on a parallel course. She immediately increased speed to full and made a 150° turn to the north in order to come around to the rear of the two Germans, to be in a position to shadow. The initial sighting from Suffolk was not received by the C-in-C in the King George V for several minutes.
Soon after sighting, Suffolk switched on her Type 284 gunnery radar and began tracking the enemy ships. At first sighting. Bismarck’s speed was 20 knots; by 1954 this had increased to 28 knots. By 2000, Suffolk was in her shadowing position off Bismarck’s port quarter, which was unseen in the mist.
Suffolk was transmitting position reports frequently. From 1922 to 2026, six position reports were sent by radio, none of which were received by Tovey in the battleship.
Suffolk re-sighted Bismarck at 2028 at a distance of 10 miles; she immediately turned away to the north-east to open the range and get back into the mist.
2031. Bismarck opened fire with 15in guns on Suffolk, and Prinz Eugen opened fire on the Norfolk. Neither of the two British cruisers took damage. The range was 10,000 to 12,000 yards.
2033. The two cruisers began to shadow from fine on the quarter. Speed was 28 knots.
2154. The Bismarck entered a rainstorm and passed out of sight. Suffolk maintained contact by radar.
At 2254 the enemy was re-sighted and four minutes later Bismarck fired on a British reconnaissance aircraft. Norfolk was sighted 10 miles to port of Suffolk at 2352.
See British Cruiser Warfare: The Lessons of the Early War 1939–1941 for a day by day history of the individual actions of cruisers during this period, and much additional material on naval warfare at this time.