Wendell Fertig was born on December 16, 1900 in La Junta, Colorado. He was an engineering student at the Colorado School of Mines, and after graduation he married his wife, Mary. He and his family moved to the Philippines, where he worked as a civil engineer. He had a reserve commission in the Army Corps of Engineers, and he was called to duty on June 1, 1941 in the capacity of reserve captain. He first served as an assistant engineer in the Bataan Field Area and then as an engineer in the Northern Luzon area. He became Chief of the Construction Section at General Headquarters in November 1941. Fertig's family returned to the United States as a precautionary measure.
When the Japanese attacked the Philippines in December, Fertig destroyed supplies which had been left behind on Bataan by the American forces. As a Lieutenant Colonel, he helped General William Sharp on Mindanao beginning at the end of April, 1942 by overseeing the destruction of the main transit areas to keep the Japanese from using them.
Although he was ordered to take the last plane out and guide the pilot, a Navy man, to Cagayan de Oro, the pilot did not listen to his directions and ended up landing in a fish trap. A bomber arrived the next day to take evacuees to Australia, but Fertig did not have a sufficient rank to join them, so he was told to say behind and surrender himself to the Japanese. However, he decided not to give himself up. Instead, he kept tabs on the military situation in Mindanao, and on September 12, 1942, the leader of one of the local guerrilla groups approached Fertig and asked him to become the commanding officer in order to dispel the rivalry among the groups.
However, he felt that having two other colonels in charge, in addition to himself, would not work out, so he promoted himself to brigadier general and made silver coins. He also cut out stars with tin snips and soldered safety pins to them. He used his engineering ingenuity to manufacture his own supplies, including a radio, which put his guerrilla force in touch with the Navy in San Francisco. In February 1943, Fertig was appointed Commanding Officer of the 10th Military District on Mindanao by MacArthur, and he was ordered to relay information on Japanese activities to Australia but not to engage in any attacks. He did not agree to the latter, and over the next two and a half years he initiated and took command of the Mindanao section of the United States Forces in the Philippines. As such, the group organized raids against the Japanese Occupied Forces on Mindanao.
Fertig received a promotion to Colonel in August 1943. He also received the Distinguished Service Cross. The United States Forces in the Philippines became one of the most effective irregular units in World War II. When American forces arrived in March 1945, Fertig's guerrillas took part in the Battle of Mindanao, which ended on August 15, 1945 with the successful abolition of Japanese resistance on the island.
After the war, Fertig served as the officer-in-charge of ROTC at his alma mater, the Colorado School of Mines, for four years; he was a professor of military science and tactics. He received the Distinguished Service Medal in May 1946, and he directed the Army's jungle warfare training. He also helped found the Army Special Warfare School in North Carolina. He served as a consulting engineer and ran a Colorado mining company until his death on March 24, 1975.