In February 1936, his daughter Hilary was born. Fuchs organised an expedition to investigate the Lake Rukwa basin in southern Tanzania in 1937. He returned in 1938 to find that his second daughter, Rosalind, had severe cerebral palsy. Rosalind died in 1945. His son, Peter, was born in 1940.
At the age of thirty, he enrolled in the Territorial Army, and was dispatched to the Gold Coast from 1942 to July 1943. He returned home and was posted to London at Second Army headquarters in a civil affairs position. The Second Army was transferred to Portsmouth for the D-Day landings, and Fuchs eventually reached Germany in time to see the release of prisoners from the Belsen concentration camp. He governed the Plön district in Schleswig-Holstein until October 1946, when he was discharged from military service with the rank of Major.
Fuchs was involved with the Falkland Islands Dependencies Survey (now the British Antarctic Survey) beginning in 1947, when he applied for a geologist position. The organization's goal was to promote Britain's claims to Antarctica, and secondarily to support scientific research. In 1950 Fuchs was asked to develop the new London scientific bureau of the Survey, to plan research in the Antarctic and support research publication. He would eventually become director of the Falkland Islands Dependencies Survey, from 1958 (after his return from the successful Antarctic expedition) until 1973. His wife died in 1990 of a heart attack. The next year, he married Eleanor Honnywill, his former personal assistant at the British Antarctic Survey. Sir Vivian Fuchs died on 11 November 1999, at the age of 91.
Fuchs is best known as the leader of the Commonwealth Trans-Antarctic Expedition, a Commonwealth-sponsored expedition that completed the first overland crossing of Antarctica. Planning for the expedition began in 1953, and envisioned the use of Sno-Cat tractors to cross the continent in 100 days, starting at Weddell Sea, ending at Ross Sea, and crossing the South Pole. Fuchs and his party arrived at Antarctica in January 1957 after camp had been set up. The party departed from Shackleton Base on November 24, 1957. During the trek, a variety of scientific data were collected from seismic soundings and gravimetric readings. Scientists established the thickness of ice at the pole, and the existence of a land mass beneath the ice. On March 2, 1958, Fuchs and company completed the 99-day trip by reaching Scott Base, having travelled 2,158 miles.
The Fuchs Medal was created in 1973 for "Outstanding devotion to the British Antarctic Survey's interests, beyond the call of normal duty, by men or women who are or were members of the Survey, or closely connected with its work."
The medal is awarded to 1 or 2 people per year for their contribution to the British Antarctic Survey.