In September 1945 Christison deputised for Admiral Lord Louis Mountbatten as commander of South East Asia Command, and took the surrender of the Japanese Seventh Area Army and Japanese South Sea Fleet at Singapore on 3 September.
Pada bulan September 1945, Christison mewakili Lord Louis Mountbatten sebagai komandan SEAC dan menerima penyerahan Angkatan Darat Wilayah VII Jepang dan Armada Laut Selatan Jepang di Singapura pada tanggal 3 September.