On the Agueda Massena could not subsist. He retired to Salamanca, where he was in communication with Marshal Bessières, who commanded a great force called the Army of the North. Wellington then invested Almeida, thinking it was provisioned only for a fortnight, yet it was still resistant the latter end of April, when the Prince of Essling, having reorganized his army and obtained cavalry and guns from Bessières, came down to raise the blockade. The English general, not expecting this interference, had gone southwards to superintend the operations of Marshal Beresford, but he returned rapidly when he heard of the French movement, and fixed on a field of battle between the Agueda and Coa. There the ground, though open and fit for cavalry, was traversed from east to west by three nearly parallel rivers, the Azava, Duas Casas, and Turones; the first considerable, and all having, in common with the Agueda and Coa, this peculiarity, their channels deepen as the water flows: mere streams with low banks in their upper courses, they soon become foaming torrents rushing along rocky gulfs. Almeida, situated on high table-land between the Turones and Coa, was closely blockaded, the light division and the cavalry were on the Azava covering the investment, the rest of the army was cantoned in the villages behind them. Swollen and unfordable was the Azava, and two thousand French attempted to seize the bridge of Marialva on the 24th, but the ground was strong, and they were vigorously repulsed by Captain Dobbs of the 52nd, though he had but a single bayonet-company and some riflemen. Next day Massena reached Ciudad Rodrigo in person, and the 27th he felt the light division posts from Espeja to Marialva. On the 28th Wellington arrived, and took position behind the Duas Casas.