Giovanni de Medici (1498-1526) was the most able soldier produced by the Medici family, and was the father of Cosimo I, the first grand duke of Tuscany.
Giovanni was born into the younger branch of the Medici family, descended from Lorenzo, brother of Cosimo the Elder, founder of the senior branch of the family. During Giovanni's lifetime the younger branch was fairly insignificant, but he began the process of raising its profile. His father was another Giovanni de Medici, the grandson of Lorenzo. Giovanni was originally christened Lodovico, but after his father's early death took his name. His mother was Caterina Sforza, a member of a successful Italian military family.
Early in his career he became known as Giovanni delle Bande Nere, Giovanni of the Black Bands, after his men began to carry black banners to mourn the death of Leo X.
Like most Italian mercenary commanders of the period Giovanni served each side in the Italian Wars. In 1516-17 he fought for Pope Leo X in his conflict with Francesco Maria della Rovere. In 1521 he fought for Leo X during the first French invasion of Italy in the First Hapsburg Valois War, taking part in the campaign that ended with the French loss of Milan.
In 1522 he fought at Colonna's great victory of Bicocca (27 April 1522), which saw the defeat of a renewed French invasion.
In 1523 Giovanni fought in the Imperial Army, first under Colonna, then under Charles de Lannoy. He helped to defeat an advance by the Grisons, French allies from the Alps, undermining their chances of defending Milan. He fought on the Imperial side at the battle of the Sesia (April 1524), where the famous Bayard was killed.
In 1525 he turned to the French service when his cousin Pope Clement VII came to terms with Francis I. He fought on the French side during the siege of Pavia, but suffered a wound in the foot before the disastrous battle of Pavia (24 February 1525) and so wasn't involved in that French defeat.
In 1526 Giovanni joined the anti-Imperial army of the League of Cognac (Second Hapsburg-Valois War), serving under Francesco Maria della Rovere, Duke of Urbino. The League was a disastrous failure, and in the following year Rome was sacked by an out-of control Imperial army. By then Giovanni was dead. He was fatally wounded in fighting against German reinforcements under Georg von Frundsberg at Borgoforte near Mantua on 25 November 1526 (although the wound was actually caused by a Ferrarese cannon ball) and died on 30 November at Mantua after gangrene set in despite his having his leg amputated.
Giovanni married Maria Salviati and they had one son, Cosimo (1519-74). By now the senior branch of the family was close to dying out. In 1532 Pope Clement VII, a member of that branch of the family, installed Alessandro de Medici, possibly his own illegitimate son, as Duke of Florence, but Alessandro was a brutal ruler who was assassinated in 1537. This left the way open to the young Cosimo (still under 20 at the time), who became Duke of Florence, bringing the junior branch of the family to power. In 1569 Cosimo became Grand Duke of Tuscany as Cosimo I, establishing a dynasty that lasted until 1738.