Selected for a military command by Charles V, he took part in the siege of Tunis (1535), and successfully defended Perpignan against the dauphin of France. He was present at the battle of Mühlberg (1547), and the victory gained there over John of Saxony was due mainly to his exertions. He took part in the subsequent siege of Wittenberg, and presided at the court-martial which tried the elector and condemned him to death.
In 1552 Alva was intrusted with the command of the army intended to invade France, and was engaged for several months in an unsuccessful siege of Metz. In consequence of the success of the French arms in Piedmont, he was made commander-in-chief of all the emperor's forces in Italy, and at the same time invested with unlimited power. Success did not, however, attend his first attempts, and after several unfortunate attacks he was obliged to retire into winter quarters.
After the abdication of Charles V he was continued in the command by Philip II, who, however, restrained him from extreme measures. Alva had subdued the whole Campagna and was at the gates of Rome, when he was compelled by Philip's orders to negotiate a peace.
In 1567, Philip, who was a bigoted Catholic, sent Alva into the Netherlands at the head of an army of 10,000 men, with unlimited powers for the extirpation of heretics. When he arrived he soon showed how much he merited the confidence which his master reposed in him, and instantly erected a tribunal which soon became known to its victims as the "Council of Blood," to try all persons who had been engaged in the late commotions which the civil and religious tyranny of Philip had excited. During the six years of his governorship, no less than 18,000 people were executed. He imprisoned the counts Egmont and Hoorn, the two popular leaders of the Protestants, and had them condemned them to death.
His attempt to raise money by imposing the Spanish alcabala, a tax of 10 % on all sales ("tenth penny" tax), aroused the opposition of the Catholic Netherlands themselves. The exiles from the Low Countries, who called themselves Geuzen (French gueux, "beggars"), encouraged by the general resistance to his government, fitted out a fleet of privateers, and after strengthening themselves by successful depredations, seized the town of Den Briel (Brielle). Thus Alva by his cruelty became the unwitting instrument of the future independence of the seven Dutch provinces.
The fleet of the exiles, having met the Spanish fleet, defeated it, and reduced North Holland and Bergen. The States-General, assembling at Dordrecht, openly declared against Alva's government, and marshalled under the banners of the prince of Orange.
Alva's preparations to oppose the gathering storm were made with his usual vigour, and he succeeded in recovering Bergen, Mechelen and Zutphen, under the conduct of his son Don Frederick. With the exception of Zealand and Holland, he regained all the provinces; and at last his son stormed Naarden, and massacring its inhabitants, proceeded to invest the city of Haarlem,which, after standing an obstinate siege, was taken and pillaged. Their next attack was upon Alkmaar; but there they were met with such desperate resistance that they were constrained to retire.
Alva's feeble state of health and continued disasters induced him to solicit his recall from the government of the Low Countries. In December 1573 Philip accepted his resignation and replaced him with Luis de Zúñiga y Requesens.
On his return he was treated for some time with great distinction by Philip, till a love affair of Don Frederick dragged father and son into disgrace. Alva was banished from court and confined in the castle of Uzeda.
Here he had remained two years, when the success of Don Antonio in assuming the crown of Portugal determined Philip to turn his eyes towards Alva as the person in whose fidelity and abilities he could most confide. Appointed to the supreme command in Portugal in 1581, Alva soon defeated Antonio, drove him from the kingdom, and reduced the whole under the subjection of Philip. Entering Lisbon he seized an immense treasure, and allowed his soldiers to sack the suburbs and vicinity.
Alva, however, did not enjoy the honours and rewards of his last expedition, for he died at Thomar in January 1583.
This entry is based on the 1911 Encyclopeadia Britannica article. Update as necessary.