In September 1945, a few days after The Republic of Indonesia proclaimed its independence, the Allied army who were assigned to disarm the Japanese army and control the internees in several areas of Indonesia was in conflict with the Republic of Indonesia. Even in Surabaya (East Java) the conflict led to an open war. Using historical method with primary and secondary sources, this research looks at the solidarity among members of Nahdatul Ulama in their struggle to defend Surabaya city at the beginning of the Indonesian independence.