During the Spanish Civil War, Springhall served as the first political commissar of the British Battalion of the XV International Brigade,^[4][5] later becoming Assistant Commissar of the XV International Brigade. Although politically experienced, he was described as "a pleasant, but hopelessly obtuse and humourless man ... he seemed to be a well-intentioned man who was completely out of his depth in the position in which he found himself".^[6] On 12 January 1937, following the Battle of Lopera and tensions between British and Irish volunteers, he called a meeting to discuss the issue. The stormy meeting resulted in the Irish volunteers voting to join the Abraham Lincoln Battalion. The meeting may have been a political miscalculation, but Irish volunteers saw it as a deliberate stunt by British Communists to ruin the chances of forming an Irish national unit. Springhall later admitted he was glad the Irish group had left, but he was blamed by many senior communist figures for a "grave political mistake".^[7] Although he was shot at the Battle of Jarama, on 27 February 1937,^[8] the bullet passed through his cheeks and he was not seriously wounded. He returned to the UK in 1938.

On his return to the UK he became editor of the Daily Worker, then briefly served as the CPGB's representative in Moscow. He returned to the UK again to ensure that the party supported the Molotov–Ribbentrop Pact.^[9] General Secretary Harry Pollitt opposed this and was removed, Springhall working as National Organiser to lead the party alongside Rust and Rajani Palme Dutt.^[1] The British government were concerned in early 1940 having seen copies of secret lecture notes by Springhall urging comrades in the armed forces to "initiate all effective actions against the war".^[10] MI5 reported that Springhall was a "dangerous type of Communist agitator" and exempted from military service as he would "certainly constitute a serious menance to morale and discipline" in the armed forces.^[11]

In 1943, Springhall was caught receiving secret documents from Olive Mary Sheehan, a clerk in the Air Ministry telecommunications office, who was also cadres leader of the secret Air Ministry group of the Communist Party. After his arrest and interrogation by MI5, he was found guilty under the Official Secrets Act on 28 July 1943 of obtaining "for a purpose prejudicial to the safety or interests of the State information which might be useful to the enemy". He was given a seven-year prison sentence. He was thought to have been spying since 1941.^[12] He was subsequently removed from his party posts.^[1] It subsequently emerged that he had also obtained classified information from Ormond Uren of the Special Operations Executive.^[2] He served four-and-a-half years of a seven-year penal servitude sentence. On his release, he worked in advertising before travelling through Eastern Europe to China, where he worked as an advisor to the Chinese Information Bureau of the Press Administration. He travelled to Moscow in 1953 to receive treatment for throat cancer, but died there aged 52.^[1] His grave is located at the Babaoshan Revolutionary Cemetery in Beijing.