The First Hapsburg-Valois War (1521-26) was the start of a quarter of a century of conflict between Francis I of France and the Emperor Charles V and ended with the disastrous French defeat at Pavia in February 1525), which saw the French position in Italy collapse, never really to recover (Italian Wars, 1494-1559).
The was is known by a variety of names, including the Fourth Italian War and the First Italian War between Charles V and Francis I, but significant campaigns took place outside Italy and the wars ended after the deaths of both monarchs, and so we are going to use the more common Hapsburg-Valois War.
At the start of the war both camps had a foothold in Italy. Francis I had secured his control of Milan during his First Invasion of Italy (1515-16), in many ways the high point of his Italian adventures. Charles V inherited the kingdoms of Naples and Sicily in the south of Italy. In the centre the Papal States formed a rather chaotic block, although Pope Julius II (ruled 1503-1513) had increased the level of Papal power in the area. A number of independent states still survived, including Florence, then dominated but not officially ruled by the Medici, and the Venetian Republic.
A key element in the outbreak of the series of Hapsburg-Valois Wars was the appearance of the massive personal empire of Charles V. In 1516 Ferdinand of Aragon died, and the young Archduke Charles inherited Castile, Aragon, Naples, Sicily, the Netherlands, the Franche-Comté and the expanding Spanish empire in the Americas. In 1519 the Emperor Maximilian died, and Charles inherited the Hapsburg lands in Eastern Europe (although his brother Ferdinand was given day-to-day power in Austria). Charles and Francis I of France then became rivals for the vacant Holy Roman throne, but in June 1519 Charles was elected to the throne, giving him some power across Germany, but also putting him the front line of the fight against the Protestant Reformation, which began to emerge as a serious problem early in his reign.
The Treaty of Noyon (13 August 1516), which had ended the previous war, appeared to have resolved most issues between Charles and Francis, with Charles surrendering his claims to Milan and Francis his claim to Naples. However the transfer of these rights wasn't straightforward. The French claim to Naples was to pass to Charles through his planned marriage to Louise, daughter of Francis I. Sadly Louise died in 1517 at the age of two. In 1518 she was succeeded as Charles' fiancée by her younger sister Charlotte, but she died in 1524, just before turning six. In 1526 Charles married his cousin Isabella of Portugal, so the clauses surrendering the French claim to Naples were never implemented. In return Charles would eventually renew his claims to Milan and to Burgundy.
War between Francis and Charles was probably inevitable. Charles certainly put some effort into gaining allies. In May 1521 he agreed alliances with Pope Leo X, and with Henry VIII of England. The treaty with England expected war to begin in 1523.
By this point fighting had already begun around the borders of France. In the north-east Robert de la Marck, Duke of Bouillon, invaded Luxembourg, while Charles, Duke of Gelders, campaigned in the Netherlands.
In the south-west Henri d'Albret, the deposed king of Navarre, invaded his lost kingdom with French support (the French contingent was led by André de Foix). The French captured Pamplona (Ignatious de Loyola, future founder of the Jesuits, was wounded during the defence of the city). Henri was installed on the throne, but his troops were then defeated by the Spanish at the Battle of Esquiroz (near Pamplona, 30 June 1521), and he was driven back into France.
In the autumn an Imperial army of up to 35,000 men, lead by Count Henry of Nassau, invaded eastern France. The fortress of Mouzon fell after a brief siege, and Nassau moved on to Mézières. If this fortress fell then Champagne would have been exposed to an Imperial invasion, but the garrison of 1,000 was commanded by Pierre Terrail, seigneur of Bayard. He was able to hold the fortress for a crucial period, until Francis I was able to appear with the main French army.
The fighting soon spread to Italy. It began with a failed siege of Parma, carried out by a Spanish-German-Papal Army commanded by Prospero Colonna. Colonna then abandoned the siege and instead concentrated on the French army in Milan, commanded by Odet de Foix, Vicomte de Lautrec. The French were out-manoeuvred and on 19 November 1521 the Imperial forces captured Milan. Francesco Maria Sforza was installed as the new Duke of Milan. Lautrec escaped east to Como, where he took shelter with France's Venetian allies. The only glimmer of hope for the French was that they retained Milan castle, which had to be besieged.
By the end of the first year of war things were going badly for Francis. His border campaigns had failed, and his main foothold in Italy had been lost. The main French success of the year had been the defeat of the Imperial invasion of Champagne.
1522 wasn't a good year for French arms. Early in the year Lautrec was reinforced, bringing his army up to around 25,000 men, along with 10,000 Venetians. However his Swiss troops were discontented and unpaid and insisted that he attacked quickly or they would leave. Lautrec decided to attack Colonna in a prepared position outside Milan, and the French suffered a heavy defeat at the battle of Bicocca (27 April 1522). Once again Lautrec was forced to retreat east into Venetian territory.
On 30 May 1522 an Imperial army commanded by Colonna and the Marquis of Pescara captured Genoa in a sudden assault (in response the capable Genoese Admiral Andrea Doria entered the service of Francis I). This removed the last major French possession in northern Italy.
The Imperial successes in Italy encouraged the English to side more firmly with Charles. In the summer of 1522 Charles V visited England on his way from the Netherlands to Spain, and on 19 June Charles and Henry agreed the Treaty of Windsor. This called for a joint invasion of France, to be carried out in 1524.
In the short term the English fleet combined with a Spanish fleet to raid the French coast. Later in the year the Earl of Surrey, supported by the Count van Buren, raided into Picardy from Calais. Surrey was later replaced by the Duke of Suffolk, but neither commander had any great success.
1523 began badly for Francis. The vast duchy of Bourbon had passed to Count Charles of Montpensier, Constable of France, by marriage. When his wife Susanne died without producing an heir, Charles's claim to the duchy was damaged. Both Francis I and his mother advanced claims against different parts of the Duke's inheritance. The Duke assumed that he wouldn't get a fair hearing at the Parliament of Paris, and instead offered his services to Charles V. In the long run he wasn't quite as valuable an ally as the Emperor might have hoped, but in 1523 his change of sides did delay preparations for a fresh French invasion of northern Italy.
When the invasion did finally begin Francis felt unable to risk leaving France, and so the command passed to Admiral Guillaume de Bonnivet. In September Bonnivet captured Novara, but he was then pinned down in that area by the Imperial forces under Prospero Colonna. At the same time Venice made peace with Charles V, so the French lost their main ally in Italy. Bonnivet decided not to try and storm Milan, and instead prepared for a long siege. This lasted to the end of the year, before the French were forced to pull back to the Ticino.
Elsewhere a British and Imperial invasion of Picardy made little or no progress, while a Spanish invasion across the Pyrenees late in the year came close to Bayonne before being forced to retreat.
Over the winter of 1523-24 the able Imperial commander Colonna died. He was replaced by Charles de Lannoy, viceroy of Milan, with the Marquis of Pescara as his main military commander.
Lannoy and Pescara were able to force the French into a retreat. The key moment came when Bonnivet attempted to move from Novara to the Sesia River to join up with Swiss reinforcements. During the retreat Bonnivet was wounded, and command passed to the famous French leader Pierre Terrail, seigneur of Bayard (1475-1524). Bayard attempted to rally the French rearguard but was killed by an arquesbus ball at the battle of the Sesia (30 April 1524). The remnants of the French army did manage to escape, but the loss of Bayard was a heavy blow.
After this success Charles and Henry VIII agreed a new plan. Charles of Bourbon was to invade southern France from Italy. A joint English-Imperial force was to attack from Picardy. Finally a Spanish army was to invade via Roussillon in the south-west.
Bourbon's invasion began on 1 July. By August he was outside Marseille, but his campaign stalled there. The French had a strong garrison in the city, and had the support of Andrea Doria, the Genoese naval commander. The siege of Marseille was lifted late in September and the Imperial forces retreated back across the Alps.
By now Francis I had arrived in the south of France with the main Royal army. He decided to chase the retreating Imperials back into Italy. The Imperial forces decided to try and hold on to a number of fortresses, including the castle of Milan, the strong fortress at Alessandria, and most famously Pavia. Milan fell easily to Francis, and the main Imperial army retreated to Lodi. At this point Francis made a crucial mistake. Instead of focusing his efforts on the weakened Imperial army he decided to besiege Pavia. The siege works began early in November, but the city held out.
French success encouraged Pope Clement VII to change sides and sign a new treaty with Francis I (12 December 1524). This treaty would lead to defeat for Francis and disaster for the Pope, who would soon see Rome sacked by an out-of-control Imperial army. In the short term it encouraged Francis to divide his forces, sending 11,000 men under John Stuart, second duke of Albany, south to conquer Naples. These troops would be badly missed at Pavia, and would achieve nothing in the south of Italy.
The successful defence of Pavia gave Charles the time he needed to raise reinforcements in Germany, and by late January 1525 Lannoy and Pescara commanded a powerful Spanish-Italian-German army. The decisive battle of the war came on 24 February 1525 (Battle of Pavia). On the night of 23-24 February the Imperial army outflanked the French defensive positions. On the morning of 24 February the two sides clashed. Francis attempted to win time for his army to redeploy to face the new threat, but he failed. Worse was to come - Francis I was captured and his army was destroyed. Elsewhere the news caused Albany's army to break up, and the Duke had to escape to France by sea.
Francis was eventually taken to Madrid, where he was imprisoned. For some time he resisted all pressure to make concessions, and came close to abdicating, but eventually he was forced to sign the Treaty of Madrid (14 January 1526). Under the terms of this treaty he was to marry Charles's sister Eleonora. He renounced all rights to Milan, Naples, Genoa and Asti in Italy, and Flanders, Artois, Tournai, and the duchy of Burgundy on the French borders. He also abandoned the d'Albret claim to Navarre. His two eldest sons were kept as hostages. The Duke of Bourbon was to be restored to all of his lands and posts.
The Treaty of Madrid led to the shortest period of peace during the entire Italian Wars. Francis was released on 17 March 1526, and on 22 May 1526 he formed the League of Cognac, an alliance with Pope Clement, Florence, Venice and even Francesco Sforza, duke of Milan. Henry VIII of England encouraged the new league but didn't join it. By the summer of 1526 open warfare had broken out in Italy, marking the start of the Second Hapsburg-Valois War or the War of the League of Cognac (1526-30).