My question pertains to any and all military historians (it will be even better if you are a professor in a military academy). The Great War had provided a wealth of lessons and new military equipment that set the precedent for future wars. The tactics of Trench Warfare and the Creeping Barrage left behind valuable tactical legacies that would eventually be phased out due to the more modern and mobile warfare that we would see during World War II. World War II was a completely different beast from its sister conflict and while we would see instances of Trench Warfare such as in the Eastern Front during Barbarossa and the Soviet Counter Offensives the year after, it was rare and the massive defensive capabilities of trenches were nullified when tanks were used en masse such as in Blitzkrieg and Soviet human wave tactics.
So, my question(s) is: was there a giant reflection that took place after 1918 in which several military theorists made sure to not make the same tactical mistakes that they made from 1914 to 1918? Was this reflection a shared effort or was it primarily an individual effort from several military theorists? Who were some of the leading theorists that changed the way future wars would be fought? Did any of the previous Old Guard who fought in the Great War have a hand in producing those new theories?
Some things change slowly, perhaps because technology doesn't advance quickly enough, or strategic and tactical teachings don't change rapidly enough. The French Maginot Line is learning the wrong answers, whilst Blitzkrieg is learning the right answers, at least in part.
Field Marshall, Sir Douglas Haig held fast to his belief in mounted troops, albeit, perhaps not cavalry and the 'armee blanche' concept. He was not alone as US and Australian military doctrine ascribed roles to mounted cavalry and Light Horse right up until 1941. German cavalry played an important role in the invasion of Poland and France in 1939 - 40.
The importance of air power was recognised witnessed by the establishment of regular air forces containing specialist aircraft to cover fighter, reconnoitring, light bomber, and heavy bomber roles. For the development of air power in the post-WW1 era read about Italian, Giulio Dohet.His book, ‘Command of the Air’ was first published in 1921 and a revised version came out in 1927. It was regarded as a classic by early airpower theorists and had a major impact in shaping and development of air power especially in USA and Britain. He argued that command of air should be the first objective during war, and having achieved it, subsequent bombing of industrialised and population centres would be so disruptive and destructive that the enemy would be forced to sue for peace. He maintained that control of the air followed by strategic bombing could win a war independent of land and sea power. He is regarded as the father of airpower.
Also examine General Trenchard (RAF) and USA Col. Billy Mitchell.
Captain Sir Basil Henry Liddell Hart and Major-General John Frederick Charles Fuller both advocated the widespread use of mechanisation in modern warfare which is seen, by some, as the birth of Blitzkreig. Use of tanks in battle varied enormously with no clear answer to what was needed as armies developed infantry support tanks, light tanks, heavy tanks, etc. The doctrinal use of tanks was equally varied and their combination with tactical airpower little appreciated, despite examples such as the Battle of Hamel, and Gen Monash's multiple arms approach to modern warfare in July, 1918.
At sea there was clearly a recognition that submarines would play in the future without truly recognising their potential, and the beginnings of air power at sea with early aircraft carriers. These developments would take time to mature into something usable by 1939.
Brief, but I hope this helps.