1920, the Royal Navy established a special anti-submarine school "HMS Osprey" in Portland, which marked the establishment of a new form system of naval warfare-submarine hunting. Walker immediately became the first batch of students who volunteered to join the school. At that time, the anti-submarine department was just established, the system was not perfect, the number of personnel was small, and the promotion opportunities were slim. Compared with those high-sounding "big ships and huge guns" departments, this place is simply a "hinterland", but far-sighted Walker did not hesitate to choose to work for this department, because he knew that once Britain went to war with Germany again, submarine hunting in the Atlantic would safeguard the security of the whole Britain. Since 1925, Walker has been stationed on the battleships HMS Revenge, HMS Nelson and HMS Queen Elizabeth as anti-submarine officers of the fleet, but his career in serving on the big ship disappointed him because his enthusiasm for submarine warfare was not understood. Finally, at 1933, Walker, who has been promoted to lieutenant colonel, got a chance to display his talents. He was appointed as the captain of the old S-class destroyer HMS Shikari D.85, which has been equipped with ASDIC. However, this exciting position of Walker only lasted for six months, because he was transferred to China Sub-fleet to command HMS Fall L.34, which was used as a special yacht for the commander of China Sub-fleet. Obviously, this appointment made Walker feel uneasy again, but he still tried his best to do his job well, but he was still criticized by some people. This forced him to temporarily retreat at 1937 and return to the anti-submarine school "Osprey" in Portland as a teacher, responsible for studying anti-submarine tactics until the outbreak of World War II. Although he lost the opportunity to be promoted to colonel, he was still able to engage in his favorite career. More importantly, when he works on shore, he can go home every day.
After the outbreak of World War II, Walker was stationed in Dover Port as the staff officer of Vice-ADM vice admiral, and was responsible for the safety of transporting expeditionary forces to France through the English Channel. 1940 the Norwegian campaign and Dunkirk retreat caused Britain to lose nearly 30 escort ships, and the operation of the escort fleet in the Atlantic Ocean faced an unprecedented dark period. Walker paid close attention to the development of the Atlantic war situation anxiously, and applied in March of 194 1, hoping to join the Atlantic escort and anti-submarine warfare, thus contributing his hard work for many years. Under the recommendation of General Ramsey, Walker finally got the attention of ADM. Percy Noble, the commander-in-chief of the West Haikou Command at that time. In September of that year, Walker was appointed as the captain of HMS Stork U.8 1, a Medak-class light frigate, and led the 36th escort formation, except for the Stork. It also includes city-class light frigate HMS Deptford U.53 and seven flower-class diving speedboats HMS Rhododendron K.78, Marigold K.87, Morning Glory K.45, Carved Bell Willow (HMS Pentstemon K.6 1), Gardenia K.99, and St. The hidden anti-submarine expert Walker finally has a chance to show his talents.