Military
Hence, Clausewitz placed political aims above military goals, ensuring civilian control of the military. Military strategy was one of a triumvirate of 'arts' or 'sciences' that governed the conduct of warfare, the others being: military tactics, the execution of plans and manoeuvring of forces in battle, and maintenance of an army.

The meaning of military tactics has changed over time; from the deployment and manoeuvring of entire land armies on the fields of ancient battles, and galley fleets; to modern use of small unit ambushes, encirclements, bombardment attacks, frontal assaults, air assaults, hit-and-run tactics used mainly by guerrilla forces, and, in some cases, suicide attacks on land and at sea. Evolution of aerial warfare introduced its own air combat tactics. Often, military deception, in the form of military camouflage or misdirection using decoys, is used to confuse the enemy as a tactic.
A major development in infantry tactics came with the increased use of trench warfare in the 19th and 20th centuries. This was mainly employed in World War I in the Gallipoli campaign, and the Western Front. Trench warfare often turned to a stalemate, only broken by a large loss of life, because, in order to attack an enemy entrenchment, soldiers had to run through an exposed 'no man's land' under heavy fire from their opposing entrenched enemy.

Technology: As with any occupation, since ancient times, the military has been distinguished from other members of the society by their tools: the weapons and military equipment used in combat. When Stone Age humans first took flint to tip the spear, it was the first example of applying technology to improve the weapon. Since then, the advances made by human societies, and that of weapons, has been closely linked. Stone weapons gave way to Bronze Age and Iron Age weapons such as swords and shields. With each technological change was realized some tangible increase in military capability, such as through greater effectiveness of a sharper edge in defeating armour, or improved density of materials used in manufacture of weapons.
On land, the first significant technological advance in warfare was the development of ranged weapons, notably the sling and later the bow and arrow. The next significant advance came with the domestication of the horses and mastering of equestrianism, creating cavalry and allowing for faster military advances and better logistics. Possibly the most significant advancement was the wheel, a staple of transportation, starting with the chariot and eventually siege engines. The bow was manufactured in increasingly larger and more powerful versions to increase both the weapon range and armour penetration performance, developing into composite bows, recurve bows, longbows, and crossbows. These proved particularly useful during the rise of cavalry, as horsemen encased in ever-more sophisticated armour came to dominate the battlefield.

In medieval China, gunpowder had been invented, and was increasingly used by the military in combat. The use of gunpowder in the early vase-like mortars in Europe, and advanced versions of the longbow and crossbow with armour-piercing arrowheads, put an end to the dominance of the armoured knight. Gunpowder resulted in the development and fielding of the musket, which could be used effectively with little training. In time, the successors to muskets and cannons, in the form of rifles and artillery, would become core battlefield technology.As the speed of technological advances accelerated in civilian applications, so too did military and warfare become industrialized. The newly invented machine gun and repeating rifle redefined firepower on the battlefield, and, in part, explains the high casualty rates of the American Civil War and the decline of melee combat in warfare. The next breakthrough was the conversion of artillery parks from the muzzle-loading guns, to quicker breech-loading guns with recoiling barrels that allowed quicker aimed fire and use of a shield. The widespread introduction of low smoke (smokeless) propellant powders since the 1880s also allowed for a great improvement of artillery ranges. The development of breech loading had the greatest effect on naval warfare for the first time since the Middle Ages, altering the way weapons are mounted on warships. Naval tactics were divorced from the reliance on sails with the invention of the internal combustion. A further advance in military naval technology was the submarine and the torpedo.During World War I, the need to break the deadlock of trench warfare saw the rapid development of many new technologies, particularly tanks. Military aviation was extensively used, and bombers became decisive in many battles of World War II, which marked the most frantic period of weapons development in history. Many new designs, and concepts were used in combat, and all existing technologies of warfare were improved between 1939 and 1945.
During World War II, significant advances were made in military communications through increased use of radio, military intelligence through use of the radar, and in military medicine through use of penicillin, while in the air, the guided missile, jet aircraft, and helicopters were seen for the first time. Perhaps the most infamous of all military technologies was the creation of nuclear weapons, although the exact effects of its radiation were unknown until the early 1950s. Far greater use of military vehicles had finally eliminated the cavalry from the military force structure.
After World War II, with the onset of the Cold War, the constant technological development of new weapons was institutionalized, as participants engaged in a constant arms race in capability development. This constant state of weapons development continues into the present. Main battle tanks, and other heavy equipment such as armoured fighting vehicles, military aircraft, and ships, are characteristic to organized military forces.

The most significant technological developments that influenced combat have been guided missiles, which can be used by all branches of the armed services. More recently, information technology, and its use in surveillance, including space-based reconnaissance systems, have played an increasing role in military operations. The impact of information warfare, which focuses on attacking command communication systems, and military databases, has been coupled with the use of robotic systems in combat, such as unmanned combat aerial vehicles and unmanned ground vehicles.
Recently, there has also been a particular focus towards the use of renewable fuels for running military vehicles on. Unlike fossil fuels, renewable fuels can be produced in any country, creating a strategic advantage. The U.S. military has committed itself to have 50% of its energy consumption come from alternative sources.

As part of society: For much of military history, the armed forces were considered to be for use by the heads of their societies, until recently, the crowned heads of states. In a democracy or other political system run in the public interest, it is a public force.
The relationship between the military and the society it serves is a complicated and ever-evolving one. Much depends on the nature of the society itself, and whether it sees the military as important, as for example in time of threat or war, or a burdensome expense typified by defence cuts in time of peace.
One difficult matter in the relation between military and society is control and transparency. In some countries, limited information on military operations and budgeting is accessible for the public. However, transparency in the military sector is crucial to fight corruption. This showed the Government Defence Anti-corruption Index Transparency International UK published in 2013.
Militaries often function as societies within societies, by having their own military communities, economies, education, medicine, and other aspects of a functioning civilian society. A military is not limited to nations in of itself, as many private military companies (or PMCs) can be used or hired by organizations and figures as security, escort, or other means of protection where police, agencies, or militaries are absent or not trusted.

Ideology and ethics: Militarist ideology is the society's social attitude of being best served, or being a beneficiary of a government, or guided by concepts embodied in the military culture, doctrine, system, or leaders.
Either because of the cultural memory, national history, or the potentiality of a military threat, the militarist argument asserts that a civilian population is dependent upon, and thereby subservient to the needs and goals of its military for continued independence. Militarism is sometimes contrasted with the concepts of comprehensive national power, soft power and hard power.
Most nations have separate military laws which regulate conduct in war and during peacetime. An early exponent was Hugo Grotius, whose On the Law of War and Peace (1625) had a major impact of the humanitarian approach to warfare development. His theme was echoed by Gustavus Adolphus.
Ethics of warfare have developed since 1945, to create constraints on the military treatment of prisoners and civilians, primarily by the Geneva Conventions; but rarely apply to use of the military forces as internal security troops during times of political conflict that results in popular protests and incitement to popular uprising.
International protocols restrict the use, or have even created international bans on some types of weapons, notably weapons of mass destruction (WMD). International conventions define what constitutes a war crime, and provides for war crimes prosecution. Individual countries also have elaborate codes of military justice, an example being the United States' Uniform Code of Military Justice that can lead to court martial for military personnel found guilty of war crimes.
Military actions are sometimes argued to be justified by furthering a humanitarian cause, such as disaster relief operations to defend refugees; such actions are called military humanism.