The Fourth Hapsburg-Valois War (1542-44) was the last conflict between Francis I of France and the Empire Charles V, and was a drawn conflict that ended with the restoration of the pre-war status quo (Italian Wars, 1494-1559).
The Third Hapsburg-Valois War had ended as a minor French victory. The Truce of Nice of 1538 had recognised the situation at the end of the fighting, so Francis kept his conquests in Savoy, Piedmont and Artois, although he had failed in his main objective, the conquest of Milan.
The truce was meant to last for ten years, but by the start of the 1540s Francis was once again preparing for war. In 1541 two of his agents were intercepted on their way to Constantinople, where they were helping to negotiate an alliance between France and the Ottoman Empire (then ruled by Sultan Suleiman I the Magnificent). Francis also arranged an alliance with William of Cleves (sister of Anne of Cleves), and with Christian III of Denmark.
The threat of a new war with France forced Charles to launch his planned invasion of Algiers too early. The fleet set sail in October 1541, but the expedition was a disaster and was forced to return home in November.
The war started in 1542 when four French and allied armies attacked Hapsburg territory. Francis himself was in the south-west where he and the Dauphin led an attack on Perpignan, the main Spanish fortress east of the Pyrenees.
In the north-east Antoine de Bourbon, Duke of Vendome, invaded Artois and Flanders, while further south the Duke of Orleans invaded Luxemburg. The final army, under Martin von Rossem, attacked west from Cleves (just to the south-east of Arnhem).
The campaign in the south-west was halted by the Duke of Alva, who successfully defended Perpignan. In the north Orleans conquered most of Luxembourg, but then decided to move south to join his father. The Hapsburg forces in the Netherlands quickly re-conquered most of Luxembourg.
Elsewhere Christian III of Denmark entered the war against Charles, closing the Sound to traffic between the Netherlands and the Baltic. This was a big financial blow for Charles, and the blockade remained in place until 1544 when the two sides made peace.
1543 saw fighting in the north-east and on the Mediterranean coast. In the south a Franco-Turkish fleet under the Duke of Enghien and Barbarossa attacked Nice and captured the Imperial city (August 1543). The city was sacked, although the citadel held out until Imperial forces arrived by land and sea, forcing the French and Turks to leave. Barbarossa's fleet then retired to Toulon where they spent the winter, shocking Christian opinion.
At the start of the year Charles was in Spain, but in May he reached Italy. He visited the Pope, then moved north into Germany. He found troops at Speyer on the Rhine, and led them north to face Francis, who had invaded Hainault.
In September the French successfully invaded Luxembourg for a second time in two years, but Charles was also successful. He besieged and captured Duren, and on 7 September the Duke of Cleves surrendered to him. The Duke had to surrender the duchy of Gelders, and end his alliance with France, Denmark and Sweden. Charles then moved into Hainault, where he hoped to join up with an English army sent by Henry VIII, and to force Francis into a battle. On 20 October he began a siege of Landrecies, but broke it off in an attempt to catch Francis, who was nearby with a larger army. The French refused to fight, and both armies retreated into winter quarters.
Charles and Henry planned a joint invasion of France for the spring of 1544. Henry was to attack from Calais with 35,000 men, while Charles invaded Lorraine and Champagne. The two attacks were meant to be coordinated, but in the event Henry was slow getting under way.
The first significant fighting of the year actually came in Italy. Imperial forces occupied Carignano near Turin. A French army, under Francois, count d'Enghien, advanced from the French-held area of Piedmont towards Carignano. Enghien had permission to seek battle, and he defeated the Spanish at Ceresole (south of Turin) on 14 April 1544. The Spanish field army was mauled, but they still held most of the fortresses of Lombardy, and so d'Enghien was unable to make much progress. His situation wasn't improved when a force of Italian troops heading to join him was defeated by the Imperial forces at Serravalle (2 June 1544).
The Imperial invasion of France began in May 1544. Imperial forces had some early successes but then got stuck outside St. Dizier (19 June-18 August 1544). Charles himself arrived at St. Dizier on 18 July, bringing reinforcements. The French posted a sizable army nearby to try and interfere with the siege, but were unable to prevent the surrender of St. Dizier. Charles then moved to attack Chateau-Thierry and Soissons, where he arrived on 12 September.
Henry VIII didn’t get moving until mid-July. Part of his army besieged Montreuil, while Henry led most of his men to attack Boulogne, instead of moving to directly support Charles. Boulogne fell to the English on 14 September, but by then Charles was involved in peace negotiations.
On 18 September 1544 Charles and Francis agreed the Peace of Crépy. This largely restored the status-quo at the start of the war - all areas conquered since the truce of Nice were to be restored, although Francis renounced his claims to Flanders and Artois. He also renounced his claim to Naples (again). In return Charles let his claim to Burgundy slip. The treaty also included some complex marriage agreements - Charles was to provide a wife for the Duke of Orleans - either his eldest daughter, in which case she would bring the Netherlands as her dowry, or the second daughter of his brother Ferdinand, who would come with Milan.
The Peace of Crépy (and the Peace of Speyer with Denmark) left Henry VIII facing the French alone, but he was just about able to hold onto his conquests. The French came close to retaking Boulogne on 9 October (Camisade of Boulogne), but the attack failed. Intermittent warfare then continued into 1546, before England and France agreed a peace in which English possession of Boulogne was recognised.
The Fourth-Hapsburg-Valois War was the last clash between Charles and Francis. Francis died in 1547, and it would be his son Henry II who renewed the conflict in the fifth and final Hapsburg-Valois War of 1547-59. Charles would abdicate during this conflict, and the long period of conflict would be ended by the Peace of Cateau-Cambresis (3 April 1559), agreed between Henry II of France and Philip II of Spain.