From what I understand (initially from Patrick Wyman) this is a seminal text. Picking up on an idea of Michael Roberts, adjusting it and responding to later criticism from the likes of Jeremy Black. The general premise is a simple one: armies fought in one way in the 14th and 15th century and another way in the 19th century – how did the change happen? In timing, Roberts initially suggested a period of “military revolution” between 1560 and 1660, here Parker expands that to a full three centuries (1500-1800). Some critiques discussed at the end of the book suggest two revolutions – one at the start and one towards the end of that period, leaving out the century in the middle.
Anyway … the idea. Gunpowder came in, it was great at knocking down walls – so new styles of fortifications developed (bastions, ravelins, trace italienne). These forts were hard to storm (and defend) with the old small elite military, they require many men and guns. Wars became more focused on sieges, less on battles – although battles when they did occur could be decisive. New developments in naval warfare occurred as the use of cannon on board ship changed technology and tactics. All of this required money, men and supplies – feeding into the admin revolutions that occurred in Tudor England, 16th Century France and elsewhere.
Parker does go beyond Europe. The Ottomans had the technology, but were unable or unwilling to bring in the tactical changes required. Native Americans and Africans found the new fortifications impossible to deal with with their own ways of warfare (even when they did have access to guns). India soon caught up and the Marathas gave the British a tough struggle. China and Japan however had already or quickly adjusted to gunpowder and new fortifications, and were never really put to the test by europeans.
Much of the book is essentially a series of facts, stories and pieces of evidence supporting or related to this topic. This being the popular end of Parker’s work, this doesn’t get too focused. In fact, it’s a bit of a mish mash of stuff. But for the non-specialist (like me!) there are interesting stuff. If I had to pick one, the unarmed but diplomatically protected Red Seal Ships of Japan were fascinating. The last chapter puts things together and discusses place and development of the idea within the field of history.