countervallation

We learned, too, that lines of countervallation had been quietly marked out at night, with a view to attack the fort by regular approaches in case the first assault failed.

Reminiscences of Forts Sumter and Moultrie in 1860-'61 Abner Doubleday 1856

The works thrown up between the camp and besieged place are termed the _line of countervallation_, and those on the exterior side of the camp form the _line of circumvallation_.

Elements of Military Art and Science Or, Course Of Instruction In Strategy, Fortification, Tactics Of Battles, &C.; Embracing The Duties Of Staff, Infantry, Cavalry, Artillery, And Engineers; Adapted To The Use Of Volunteers And Militia; Third Edition; With Critical Notes On The Mexican And Crimean Wars. Henry Wager Halleck 1843