Military history is the field of history concerned with the study of the trends in tactics, developments in technology and the patterns of campaigns by military forces. It is a vast topic and has been consistently studied by states that draw on the lessons of history to develop their own military strategies. While warfare has advanced into its most technologically capable period in the 20th and 21st centuries, there were points in history where certain developments represented a leap forward. Each region of the world can be said to have its own unique military history based on the philosophy of those fighting, the outlook of the leadership, and the number of causes over which to launch wars. The ancient Middle East was considered to have been a fertile ground for warfare and conquests, but this was only a tiny corner of human civilization whereas other areas are considered to have been the origin of major innovations in military tactics and technology.
Much of military history has been reconstructed based on a number of sources. Primarily, there are records provided by ancient societies that emphasized the victorious exploits against other forces. Ancient Egypt recorded its military history extensively, though possibly excluded a number of non-triumphant moments in history. Additionally, metallic artifacts like weapons and armor are more commonplace than other less durable or sustainable products of the ancient world. Several epics, which today have fallen under scrutiny for their veracity, include the Iliad, the Odyssey, the Mahabharata, the Ramayana and the Bible for their military records, though many scholars have found the military aspects of these collections to be compelling, plausible and reliable.
Empires are thought to have begun with the early conquests of the eastern Fertile Crescent under the ancient Sumerians and their great King Sargon. There seems to have been a formidable period where empires began to grow and the efforts made by conquerors became more extensive. Empires rarely grew to be over one million square kilometers in size. The earliest imperial state was the Akkadian Empire of the 3rd millennium BCE. The 18th dynasty and the New Kingdom of Egypt built extensive realms from southern Sudan to Anatolia, but they were outpaced by the Persian Empire of Cyrus the Great. Alexander the Great led Macedonia to reach new imperial records, which were supplanted by the Romans within two centuries. With the advent of Islam, the Arabs caused the greatest political and religious shift in the world until that time, creating an empire from the Indus River to the Atlantic Ocean and Spain. The Caliphate was very unstable, paving the way for a series of breakups and rivalries. The empire's center weakened enough to be overrun by the Mongolians. Later, the Ottoman Empire, the culmination of the rise of Turkic tribes, became the world's dominant power. European states later created large overseas empires. The British Empire faced a number of independence struggles, eventually declining in favor of the Soviet Union and the United States, the latter now maintaining the largest military and defense budget in human history.
The philosophy of military leadership has also been extensive. Most prominent yet most ancient is the work The Art of War by Sun Tzu in the 4th century BCE. The strategies he developed helped the Wu dynasty defeat its regional enemies by employing a set of simple principles. For example, commanders maintained responsibility and fault for operations and attacked weaknesses before strong points. The work has gone through several revisions but has been adapted to many modern institutions and used as a strategy template for industry and organizations.
European standards of warfare are found in the 4th century C.E. work Epitome of Military Science by Vegetius, a Roman. Over a millennium later, the work's influence was supplanted by Machiavelli's Art of War in the 16th century. Later, Dutch strategist Maurice of Nassau and Raimondo Montecuccoli, an Italian mercenary, published their own philosophies on military strategy.
It has been hypothesized that the popularity of military strategy in the business world it owed to the shortening of military engagements. Wars in the 20th century were relatively shorter than ancient, seasonally based wars because of the decisiveness of heavy weaponry. Thus, those who might otherwise have committed their lives to fighting have become professionals.