This chapter begins by introducing the Shanghai Municipal Council's (SMC) main defence forces, the police and volunteers. It then explains the nature of the physical barriers which appeared at times of stress at the borders of the International Settlement. The chapter examines how the Council itself succeeded in both policing and collecting taxes beyond the boundaries of the Settlement, and the ways in which this extended the area that was effectively under its authority. It presents the ways in which the SMC behaved like an aggressive and defensive state to expand its borders and preserve its political autonomy. The SMC increased its powers by exerting an assumed right to govern and police both the Settlement proper and areas beyond its limits, exceeding its rights under treaty. The SMC had two of its own organizations to call on for purposes of defence, the Shanghai Municipal Police (SMP) and the Shanghai Volunteer Corps (SVC).