During the Second World War there were several “battles” that were waged over years and spanned huge distances – the air war fought over skies of Europe and Russia and the Battle of Atlantic are two great examples. The latter was fought between the U-boats of Nazi Germany and the escorts shepherding the convoys from the United States to Britain. The aim was simple. The U-boat forces wish to create an effective blockade of food and supplies to Britain and the escort command wanted to get the convoys and merchantmen through.These struggles were fought not just by groups of soldiers, sailors, and airmen but by the quantity and quality of their machines, the reach of logistics, accuracy of intelligence, and the strategy and tactics. One of the key tactics of the U-boats was to try to locate convoys and then guide in multiple U-boats (likened to a pack of wolves or wolf pack) to overwhelm the escorts and slaughter the freighters and tankers. The preferred method of attack was at night on the surface.Most people who are history buffs of WW2 know of the various technical moves made. The allies build merchant ships in prodigious numbers with the idea that they can build them faster than they could be sunk. They also launched large numbers of purpose-built convoy escorts whose armament and design was solely for anti-submarine warfare. Land based aircraft were modified to fly further (dubbed very long range or VLR) Escort aircraft carriers, tiny flat tops, adapted from tanker and merchant hulls were built to provide air cover beyond the reach of land bases. Sonar or asdic and radar were improved to help detect submarines under the surface and beyond visual range. Weaponry was improved with hedgehog squids, better depth bombs, better depth charges and air launched acoustic homing torpedoes. Finally, as many are aware, intelligence and code breaking (e.g. Enigma) played a critical role. The Germans countered with additional rotors to Enigma, U-boat tankers, improved designs, acoustic homing torpedoes, snorkels and radar detectors.While the moves and counter moves of technology and intelligence were important, a less well appreciate aspect of the struggle was the analysis and refinement of the actual tactics used by the escorts when they encountered a U-boat. This is the story described in the book.The Western Approaches Tactical Unit helped to analyze, refine, and develop tactics to use against the U-boats. They also played an important role in training escort commanders in how to use these tactics by the then novel approach of having them wargame the situations they would like face. The use of wargames is not new to WW2 armies and navies. The Prussian armies had popularized wargaming (kriegspiel) as a training tool. All of the major combatants used them to help train their officers and to rehearse and analyze their plans. What was interesting in this case was that young women in the Women’s Royal Naval Service (WRENS) played a key role in the development of these tactics and in the training of the escort commanders.It is an interesting read and the story is fascinating. It reveals aspects of the war that many people often underappreciate – that women served in many critical roles during WW2 and the importance of simulation and wargaming in training.The book has a few small quibbles. I wish the various maneuvers described (e.g. “Pineapple”, “Beta”) were illustrated. Simple line drawings would have helped. The wargaming exercises used to train the escort commanders were played in real time (each turn being about 2 minutes to force decision making) and it would have been helpful to show an illustrative game and to include an outline of the rules. These rules are I believe known and are an adaptation from the rules from Fred T. Jane’s wargaming rules and other contemporary games rules such as Fletcher Pratt’s naval wargame. There are some personal vignettes that are nice but sometimes the writing was edited in a melodramatic way. (We end one chapter with someone entering the cabin with Luger pistol, and many chapters later we learned this was not as sinister as it appeared). Sadly, many of the principals involved, especially the WRENS did not leave any substantive written accounts and with time there are few living participants left today.In brief, worth the time and would be interesting to not just military history buffs.