He visited Russia three times at the invitation of Maxim Litvinov, the People's Commissar for Foreign Affairs of the Soviet Union. These visits took place in 1926 (Odessa), and in 1936 and 1937 (Moscow).
Litvinov invited him to visit Russia three times; these trips happened in 1926 (Odessa) and again in 1936 and 1937 (Moscow), all at the Soviet Union's behest.