Arguably the most important role of the submarine, the Trafalgar class has an unrivalled capability to seek out and destroy other submarines that may pose a threat to any friendly force. It also has a well-proven capability to detect and attack surface forces. The Spearfish torpedo can be used against other submarines or surface ships. These capabilities can be used when the it is acting independently or in support of a task force. Trafalgar is used to great effect when the submarine is deployed in advance of friendly forces in order to reduce the flexibility of an opposition force by denying the use of an area or region. This is known as regional sea denial.