In 1921 Bradley signed up to work as an engineer in India under a two-year contract. During his time in India he worked in the Rawalpindi area where he worked supervising a large workshop. He was troubled by the terrible working conditions and low pay that the workers received. Once he returned to Britain in early 1923, he joined the Communist Party of Great Britain (CPGB), and became a trade union activist and a shop steward in an engineering works. He once led a successful labour strike shortly before the 1926 United Kingdom general strike. As a part of joint efforts by the CPGB and the Soviet Union to train Indian communist leaders belonging to the Workers and Peasants Party, Bradley returned to India in Autumn of 1927, travelling with fellow CPGB activist Philip Spratt to Bombay (now Mumbai). Soon afterwards, Bradley became an Executive Committee member of both the All India Trade Union Congress, the Workers and Peasants Party, and the Vice-President of a newly formed mill-workers' union which reached a membership of 50,000 by the end of 1928. He also held additional roles in trade unions dedicated to railway workers.