Capability development, which is often referred to as the military 'strength', is arguably one of the most complex activities known to humanity; because it requires determining: strategic, operational, and tactical capability requirements to counter the identified threats; strategic, operational, and tactical doctrines by which the acquired capabilities will be used; identifying concepts, methods, and systems involved in executing the doctrines; creating design specifications for the manufacturers who would produce these in adequate quantity and quality for their use in combat; purchase the concepts, methods, and systems; create a forces structure that would use the concepts, methods, and systems most effectively and efficiently; integrate these concepts, methods, and systems into the force structure by providing military education, training, and practice that preferably resembles combat environment of intended use; create military logistics systems to allow continued and uninterrupted performance of military organisations under combat conditions, including provision of health services to the personnel, and maintenance for the equipment; the services to assist recovery of wounded personnel, and repair of damaged equipment; and finally, post-conflict demobilisation, and disposal of war stocks surplus to peacetime requirements.
Arguably, the greatest invention that affected not just the military, but all society, after adoption of fire, was the wheel, and its use in the construction of the chariot. There were no advances in military technology, until, from the mechanical arm action of a slinger, the Greeks, Egyptians, Romans, Persians, Chinese, etc., development the siege engines. The bow was manufactured in increasingly larger and more powerful versions, to increase both the weapon range, and armour penetration performance. These developed into the powerful composite and recurve bows, and crossbows of Ancient China. These proved particularly useful during the rise of cavalry, as horsemen encased in ever-more sophisticated armour came to dominate the battlefield.
As the speed of technological advances accelerated in civilian applications, so too warfare became more industralised. 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. The next breakthrough was the conversion of artillery parks from the muzzle loading guns, to the quicker loading breech loading guns with recoiling barrel 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 IRT model underlying ASVAB scoring is the three-parameter logistic (3PL) model. The 3PL model represents the probability that an examinee at a given level of ability will respond correctly to an individual item with given characteristics. Specifically, the item characteristics represented in the 3PL model are difficulty, discrimination (i.e., how well the item discriminates among examinees of differing levels of ability), and guessing (i.e., the likelihood that a very low ability examinee would respond correctly simply by guessing).