History of submarines few years before the US, and paralleled subsequent US development in this area. In the 1950s, nuclear power partially replaced diesel-electric propulsion. The sailing of the first nuclear-powered submarine, the USN ""Nautilus"" in 1955 was soon followed by similar British, French and Russian boats. Equipment was also developed to extract oxygen from sea water. These two innovations, together with inertial navigation systems, gave submarines the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as the crossing of the North Pole beneath the Arctic ice cap by the USS "Nautilus" in 1958. Most of the
Farthest North 1948. On , a US Navy submarine, also named , was the first to sail under the ice pack to reach the North Pole. On , the became the first submarine to surface at the North Pole. In 1968, British explorer Sir Wally Herbert became the first person to indubitably reach the Pole on foot, having sledged from Alaska. His expedition was supported by air drops. Farthest North Farthest North describes the most northerly latitude reached by explorers before the conquest of the North Pole rendered the expression obsolete. The Arctic polar regions are much more accessible than those of