Encouraged by the Monroe Doctrine, America had taken on the role, repeatedly, of defending smaller nations in South America and in Central America from the imperialism of powerful Asian and European nations. Likewise, America defended some islands in the Pacific.
It seemed, therefore, that a large navy was the most useful form of military power. So American political leaders focused on paying for large and powerful fleets of battleships to be built. The following paragraph from a history books talks about this time around the turn of the century:
With uncharacteristic restraint, Theodore Roosevelt assessed American military policy at the dawn of a new century: “I believe we intend to build up a good navy, but whether we build up even a respectable little army or not I do not know; and if we fail to do so, it may well be that a few years hence ... we shall have to learn a bitter lesson....” Even though he had more insight into world politics than most of his countrymen, Roosevelt could not have predicted in 1900 that in less than two decades the United States would be embroiled in a world war or even that the nation would enter that war with standing forces beyond the imagination of policymakers in the nineteenth century.
As military technology modernized, the navy went from wooden ships to steel ships, from medium-sized ships to huge battleships, and from sailing ships to ships with powerful engines. The increased sophistication required “standing” military forces.
A “standing” navy or a “standing” army means having a large number of trained soldiers and sailors, and equipment for them, even during years of peace when there is no warfare. The opposite of a “standing” military is to have very few soldiers and sailors, and very little equipment, and then to try to get all of that together quickly when a war begins.
Because of the increasing complexity of military systems, it was not possible to quickly assemble an army and a navy on short notice. The nation needed to keep soldiers, sailors, and their equipment ready at all times.
The vast distances across the Atlantic and Pacific oceans kept America safe from attacks on the east coast and the west coast. Good relationships with Canada and Mexico kept America safe from the north and the south. Although there had been tensions and brief skirmishes with Mexico, there had been no threat of real war with Mexico for nearly a century. The United States felt that it did not need a large army to defend itself. It would rely on a navy for defense.
Officers in the army and navy gained knowledge about their equipment, and about tactical ways to use that equipment. This required the political leaders to trust the military more, because the politicians could not be expected to understand the technical details about the equipment and its use.
The political leader kept control over when and where the military would be used: this is called “civilian control” because a political leader is not allowed to be a member of the military, and the military leaders are not allowed to be elected to government offices. Military leaders were and are not engaged in the political process, and remain neutral in elections and in debates between political parties. Both Democrats and Republicans can trust the military, because it is neutral. Here's another paragraph from a history book:
However inadequate those forces were, they represented a fundamental change in American policy. The shift in policy produced an essential dependence upon a standing battlefleet to protect the United States from foreign invasion and reduced dependence upon coastal defense artillery and fortifications, backed by military forces. It also increased dependence upon the Navy and the regular Army for military tasks beyond the continental United States. At the same time, the political elite gained increased confidence in the skill and political neutrality of the Army and Navy officer corps and became more willing to institutionalize military advice and accept military professionalism as compatible with civilian control. Both groups shared an interest in the reform of the militia as the nation’s reserve force for land operations and the creation of federal reserve forces for both naval and military mobilization in case of a major war. They also urged the accelerated application of new technology to military operations, especially improved ordnance, the internal combustion engine, the airplane, and electronic communications.
From the early history of the United States, going back to the 1770s, reserve forces called “militias” had been maintained by local governments: by cities, counties, and states. As a result of the higher levels of technology, there was a trend toward having the national government supervise and organize reserve forces. This allowed the reserves to be trained and equipped in the same way across the entire nation, so that when needed, soldiers from Massachusetts could work efficiently with soldiers from Wisconsin, and soldiers from Connecticut could work efficiently with soldiers from Minnesota, for example.
As civilian political leaders trusted military officers, and worked with them, both groups saw that planning and developing for new technology would be an important feature of the military in the future. Horses would be replaced by trucks and tanks. Hand-carried notes would be replaced by telephones, telegraphs, and radio. Airplanes would play an important role in modern warfare.
The United States had no major wars between the end of the Civil War in 1865 and the beginning of World War One in 1914. The Spanish-American war had been a small operation. Even though there were no big wars during this era, the American military was redesigned into a more modern organization, both in terms of technology, and in terms of its management, planning, and administration.
