The two great frontier fortresses of Spain, Ciudad Rodrigo and Badajoz, were now in the hands of the French. Masséna had regained the Spanish frontier in March, after frequent combats with the pursuing enemy, and with heavy losses in men and horses, though he saved every gun except one. This retreat involved the evacuation of every place in Portugal except the fortress of Almeida. Wellington's pursuit would have been still more vigorous, but that his Portuguese troops were half-starved, and had lost discipline under intolerable privations. His next design seems to have been the recapture of the fortresses, but he was not without ulterior hopes--all too premature--of afterwards pushing on to Madrid and operating in the eastern provinces of Spain. He first invested Almeida, and, leaving General Spencer to continue the blockade, proceeded to Elvas in order to concert measures with Beresford for the siege of Badajoz. Thence he was suddenly recalled northward to repel a fresh advance of Masséna, strongly reinforced, for the relief of Almeida. The battle which followed at Fuentes d'Oñoro, south-east of Almeida, was among the most hardly contested struggles in the whole Peninsular war. It began on May 3, and, with a day's interval, concluded on the 5th. The British remained masters of the field, and claimed a somewhat doubtful victory, which at least secured the evacuation of Almeida. The garrison of that fortress blew it up by night, and succeeded, by masterly tactics, in joining the main French army with little sacrifice of life.