In the field of military theory, the operational level of war (also called operational art, as derived from , or operational warfare) represents the level of command that connects the details of tactics with the goals of strategy. In Joint U.S. military doctrine, operational art is "the cognitive approach by commanders and staffs—supported by their skill, knowledge, experience, creativity, and judgment—to develop strategies, campaigns, and operations to organize and employ military forces by integrating ends, ways, and means." It correlates political needs and military power. Operational art is defined by its military-political scope, not by force size, scale of operations or degree of effort. Likewise, operational art provides theory and skills, and the operational level permits doctrinal structure and process. The operational level of war is concerned with four essential elements: time, space, means, and purpose. Through means such as directing troops and allocating (limited) resources (among others), operational art aims to achieve political goals by producing an optimal (or at least near-optimal) generation and application of military power. For example, proposals may be generated to identify where to build defensive structures, how many, what kind, and manned by how many troops; a proposal may be accepted, or reworked. During the 20th century, the nascent field of operations research flourished as a result of military efforts to improve logistics and decision making. The operational level of war sits between tactics, which consists of organizing and employing fighting forces on or near the battlefield, and strategy, which involves aspects of long-term and high-level theatre operations, and the government's leadership. The Soviet Union was the first country to officially distinguish this third level of military thinking, when it was introduced as part of the deep operation military theory that its armed forces developed during the 1920s and 1930s and utilized during the Second World War. Background During the 18th and early 19th centuries, the synonymous terms grand tactics (or, less frequently, maneuver tactics) was often used to describe the manoeuvres of troops not tactically engaged, while in the late 19th century to the First World War and throughout the Second World War, the term minor strategy was used by some military commentators. Confusion over terminology was exposed in professional military publications, that sought to identify "...slightly different shades of meaning, such as tactics, major tactics, minor tactics, grand strategy, major strategy, and minor strategy". The term operational art was not widely used