Military history
The first indications of the countermarch technique in Europe was by Lord William Louis of Nassau (1538–1574) in the mid-1590s.
Korea also seemed to be adapting the volley technique, earlier than even the Japanese. "Koreans seem to have employed some kind of volley principle with guns by 1447, when the Korean King Sejong the Great instructed his gunners to shoot their 'fire barrels' in squads of five, taking turns firing and loading."
This was on display during what Kenneth Swope called the First Great East Asian War, when Japan was trying to take control and subjugate Korea. Toyotomi Hideyoshi (1537–1598) made a failed invasion of Korea, which lasted six years, eventually pushed back by the Koreans with the aid of Ming China. Japan, using overwhelming firepower, had many early victories on the Korean peninsulas. Though the Koreans had similar manpower, "the curtain of arrows thrown up by defenders was wiped out by [Japanese] gunfire." After the Japanese were finally pushed back in 1598, sweeping military reforms took place in Korea, largely based on updating and implementing the volley technique with firearms.

It was Qi Jiguang, a Ming Chinese General that provided the original treatise, disseminated to Koreans, that aided in this venture. In these manuals, Qi "...gave detailed instructions in the use of small group tactics, psychological warfare, and other 'modern' techniques." Qi emphasized repetitive drilling, dividing men into smaller groups, separating the strong from weak. Qi's ethos was one of synthesizing smaller groups, trained in various tactical formations, into larger companies, battalions and armies. By doing this they could "operate as eyes, hands, and feet..." aiding to overall unit cohesion.

Modern technologies: At the start of the World Wars, various nations had developed weapons that were a surprise to their adversaries, leading to a need to learn from this, and alter how to combat them. Flame throwers were first used in the First World War. The French were the first to introduce the armored car in 1902. Then in 1918, the British produced the first armored troop carrier. Many early tanks were proof of concept but impractical until further development. In World War I, the British and French held a crucial advantage due to their superiority in tanks; the Germans had only a few dozen A7V tanks, as well as 170 captured tanks. The British and French both had several hundred each. The French tanks included the 13 ton Schneider CA1, with a 75 mm gun, and the British had the Mark IV and Mark V tanks.
On December 17, 1903, the Wright Brothers performed the first controlled, powered, heavier-than-air flight; it went 39 meters (120 ft). In 1907, the first helicopter flew, but it wasn't practical for usage. Aviation became important in World War I, in which several aces gained fame. In 1911 an aircraft took off from a warship for the first time. Landings on a cruiser were another matter. This led to the development of an aircraft carrier with a decent unobstructed flight deck.
Chemical warfare exploded into the public consciousness in World War I but may have been used in earlier wars without as much human attention. The Germans used gas-filled shells at the Battle of Bolimov on January 3, 1915. These were not lethal, however. In April 1915, the Germans developed a chlorine gas that was highly lethal, and used it to moderate effect at the Second Battle of Ypres. Gas masks were invented in matter of weeks, and poison gas proved ineffective at winning battles. It was made illegal by all nations in the 1920s.
World War II gave rise to even more technology. The worth of aircraft grew from mostly reconnaissance to strategic bombing and more. The worth of the aircraft carrier was proved in the battles between the United States and Japan like the Battle of Midway. Radar was independently invented by the Allies and Axis powers. It used radio waves to detect objects. Molotov cocktails were invented by General Franco in the Spanish Civil War, directing the Nationalists to use them against Soviet tanks in the assault on Toledo. The atomic bomb was developed by the Manhattan Project and dropped on Hiroshima and Nagasaki in 1945, quickly and controversially ending World War II.
During the Cold War, the main powers engaged in a Nuclear arms race which comprised the making of atomic bombs, hydrogen bombs, and more advanced nuclear bombs. In the space race, both nations attempted to launch human beings into space, to the moon and send satellites. Other technological advances were centered on intelligence (like the spy satellite) and missiles (ballistic missiles, cruise missiles). The nuclear submarine was invented in 1955. This meant submarines no longer needed to surface as often, and could run more quietly. They evolved into underwater missile platforms.

Periods of military history: 

Prehistoric warfare: Prehistoric warfare refers to war that occurred between societies without recorded history. The Tollense valley battlefield is the oldest evidence of a large scale battle in Europe. More than 4,000 warriors fought in a battle on the site in the 13th century BC.

Ancient warfare: Much of what we know of ancient history is the history of militaries: their conquests, their movements, and their technological innovations. There are many reasons for this. Kingdoms and empires, the central units of control in the ancient world, could only be maintained through military force. Due to limited agricultural ability, there were relatively few areas that could support large communities, therefore fighting was common.
The Umma–Lagash war was one of the first wars in recorded history, fought between the Sumerian city-states of Lagash and Umma. The border conflict over the fertile Guedena region lasted for several generations.
Weapons and armor, designed to be sturdy, tended to last longer than other artifacts, and thus a great deal of surviving artifacts recovered tend to fall in this category as they are more likely to survive. Weapons and armor were also mass-produced to a scale that makes them quite plentiful throughout history, and thus more likely to be found in archaeological digs.
Such items were also considered signs of prosperity or virtue, and thus were likely to be placed in tombs and monuments to prominent warriors. And writing, when it existed, was often used for kings to boast of military conquests or victories.
Writing, when used by the common man, also tended to record such events, as major battles and conquests constituted major events that many would have considered worthy of recording either in an epic such as the Homeric writings pertaining to the Trojan War, or even personal writings. Indeed, the earliest stories center on warfare, as war was both a common and dramatic aspect of life; the witnessing of a major battle involving many thousands of soldiers would be quite a spectacle, even today, and thus considered worthy both of being recorded in song and art, but also in realistic histories, as well as being a central element in a fictional work.

Lastly, as nation states evolved and empires grew, the increased need for order and efficiency lead to an increase in the number of records and writings. Officials and armies would have good reason for keeping detailed records and accounts involving any and all things concerning a matter such as warfare that, in the words of Sun Tzu, was "a matter of vital importance to the state". For all these reasons, military history comprises a large part of ancient history.
Notable militaries in the ancient world included the Egyptians, Assyrians, Babylonians, Persians, Ancient Greeks (notably the Spartans and Macedonians), Kushites, Indians (notably the Magadhas, Gangaridais, Gandharas and Cholas), Early Imperial Chinese (notably the Qin and Han dynasties), Xiongnu Confederation, Ancient Romans, and Carthaginians.
The fertile crescent of Mesopotamia was the center of several prehistoric conquests. Mesopotamia was conquered by the Sumerians, Akkadians, Babylonians, Assyrians and Persians. Iranians were the first nation to introduce cavalry into their army.
Egypt began growing as an ancient power, but eventually fell to the Libyans, Nubians, Assyrians, Persians, Greeks, Romans, Byzantines and Arabs.
The earliest recorded battle in India was the Battle of the Ten Kings. The Indian epics Mahabharata and Ramayana are centered on conflicts and refer to military formations, theories of warfare and esoteric weaponry. Chanakya's Arthashastra contains a detailed study on ancient warfare, including topics on espionage and war elephants.

Alexander the Great invaded Northwestern India and defeated King Porus in the Battle of the Hydaspes River. The same region was soon re conquered by Chandragupta Maurya after defeating the Macedonians and Seleucids. He also went on to conquer the Nanda Empire and unify Northern India. Most of Southern Asia was unified under his grandson Ashoka the Great after the Kalinga War, though the empire collapsed not long after his reign.
In China, the Shang dynasty and Zhou dynasty had risen and collapsed. This led to a Warring States period, in which several states continued to fight with each other over territory. Philosopher-strategists such as Confucius and Sun Tzu wrote various manuscripts on ancient warfare (as well as international diplomacy).