For most strategic planners, space represents the ultimate high ground. In the same way that control of the skies added a new dimension to combat in the great wars of the 20th century, the military exploitation of space will be a defining characteristic of the 21st century. German rocket technology propelled the first unmanned systems into space during the latter stages of World War II. These systems traveled beyond the Karman line — the commonly accepted boundary between Earth and space, at around 100 kilometers altitude (62 miles). From the late 1950s onward, the ability to routinely launch manned and unmanned systems into orbit heralded a new era of competition between the Soviet bloc and the West, led by the United States.