He was the son of a railroader family who worked as a marshaling yard master for the Austrian National Railway (ÖBB) and was married with three daughters. The family had local citizenship rights in Gnigl and lived at 7 Siedlerstraße, which was near the railroad marshaling yards. Gnigl was a stronghold of the railway workers and had a Social Democratic railroader as mayor until February 1934.

KUMHART was a member of the Social Democratic Labor Party and its associated organizations, the Free Trade Union and the Republican Defense League militia, until they were smashed by the Austrian dictatorship in 1934. On February 12, 1934 the Austrian State Police found a copy of the Republican Defense League’s »emergency plan« while searching its office. It included the names of 47 activists who were supposed to mobilize resistance if an attempt were made to overthrow the republic. The names of railroaders Franz ASCHENBERGER, Josef HAIDINGER and Josef KUMHART were on the list. Like most Salzburg anti-fascists across the political spectrum all three were still members of the Roman Catholic Church.

After the Nazis took over Austria they became members of the »national railroad division« organized by Franz OFNER and Anton REINDL as part of a Communist resistance movement. Railway foreman Josef HAIDINGER was the leader of the »division« and the »national railway workshop« local. In the spring of 1941 KUMHART was recruited into this group by HAIDINGER and until the turn of the year 1941-1942 he paid monthly dues of one Reichsmark and got two Communist pamphlets to read. At the beginning of 1942 the Gestapo was able to get a »snitch«, an undercover Gestapo agent, into the resistance networks of the Communists and the Revolutionary Socialists and based on his reports they smashed the two networks and arrested their main members. At least 79 Salzburg city and state activists from the two networks, including 29 railroaders, were killed in Nazi concentration camps or prisons.

Josef KUMHART was arrested by the Gestapo on March 3, 1942 and was taken from the Salzburg State Court jail to the prison in Bavarian Landsberg am Lech before he was returned to the Salzburg State Court jail for trial. In five trials that the Vienna Superior Court held while sitting in Salzburg from November 23-27, 1942, 30 activists from the illegal Communist Party (KPÖ), all railroaders, were sentenced to 212 years imprisonment for »conspiracy to commit treason«. Two of the 30 railroaders, Josef KUMHART and Karl STEINOCHER, failed to survive the terror years. Four railroaders, Lorenz KÜNSTEL, Franz BROZ, Johann BRUCKMOSER and Ignaz GRABLER, died of their imprisonment injuries shortly after their liberation.

On November 24, 1942 Josef KUMHART was sentenced to five years imprisonment and in January 1943 he was sent to the Straubing prison in Lower Bavaria. Then, in July 1943, he was assigned to a penal unit of the SS supply agency »Organisation Todt« (OT). He was put to forced labor, became severely ill and died at age 47 on December 24, 1944 in Kevelaer (near the German-Dutch border).

His widow Maria was eligible for victims’ compensation as his survivor in liberated Austria and she died in Salzburg at age 73 in 1969. Their three married daughters, Maria, Berta and Josefa have descendants in Salzburg.