Neumann resigned on 12 September 1911. Along with Henry Martin, he had been a member of the Provisional Committee of 1911 which opposed notional Socialist MPs ever voting for reforms (the ‘WB of Upton Park affair’) and probably resigned on that issue. He was interned because of his German origin during the First World War where he met Rudolf Frank, co-founder of the "Bund Demokratischer Sozialisten", the Austrian counterpart to the SPGB. He was presumably repatriated to Germany at the end of the war and is reputed to have died in the Spartacist uprising of January 1919.