The French were active in Italy. In combination with Savoy, they tried to seize Spain’s ally Genoa in 1625, only to be driven back by the Spaniards. Two years later, the end of the direct male line of the Gonzaga family produced a contested succession for the Duchies of Mantua and Monferrato. Spanish intervention in the dispute led to a joint Savoyard and Spanish invasion of Monferrato in March 1628 in pursuit of a partition. A Spanish army besieged Casale, the capital as well as a major fortress in Monferrato and a crucial point on the western approaches on the Milanese. The French initially tried to stop this consolidation of Spanish power in northern Italy by backing the leading claimant, Charles, Duke of Nevers. He was permitted to raise troops from his French duchies and his governorships of Champagne and Brie on his own sovereign authority as Prince Souverain of Arches. The French army itself was engaged in the struggle against the Huguenots.
Nevers was able to raise 6,600 troops, in part thanks to the effort of his nephew, the Duke of Longueville. This was a pointed reminder of the extent to which what are generally understood as the `states’ of the period did not monopolise military power. At the same time, Richelieu was unimpressed by Nevers’s plan, thinking it lacking in support and preparation. As French power was at stake, the crown provided some support, although, as an opponent of Nevers, the Governor of Dauphiné in fact hindered the expedition. Advancing into Savoy, Nevers’s force was beaten in a skirmish in August 1628 and then dissolved.
Concerned about the situation in northern Italy, and in particular that Nevers might turn to Spain, Louis XIII and Richelieu decided to act after La Rochelle surrendered in October 1628. The Alpine pass at Susa was forced on 6 March 1629, a reminder that campaigning did not cease in the winter. This led Savoy to terms and the Spaniards to abandon the siege of Casale. However, the Spanish government was determined to fight on. It was unintentionally assisted by the maladroit Nevers who had mounted an attack on Lombardy from Mantua. Although he was able to raise only 2,500 men, this led to his being placed under the Imperial ban. Helped by his success against the Danes, Ferdinand II was able to send about 30,000 Imperial troops into northern Italy and in late 1629 they besieged Mantua. After a winter break, the siege was renewed in May 1630 and Mantua surrendered on 18 July. Meanwhile, the French decision to garrison Casale, rather than entrust it to Nevers, had encouraged the Spaniards to send fresh forces into the Monferrato in the autumn of 1629. Even after the war with the Huguenots had ended, the French lacked the forces necessary to defeat their opponents in northern Italy. Richelieu argued in November 1629 that 39,000 troops would be required, but the French were handicapped by the need to prepare a strong army to prevent the danger of an Austrian or Spanish attack on France from Germany.
Under Richelieu, France lacked the resources or organisation to field more than one large and effective campaign army. This is a reminder of the danger of reading from the notional total army sizes sometimes quoted and from the wide-ranging nature of hostilities and confrontation in order to assume that several effective armies could be deployed at the same time. In the case of France, as David Parrott has pointed out, ‘a military system that was geared to the fighting of short campaigns in a single theatre was finally confronted in 1630 with the reality of a very different type of war’, and found wanting. The same was true for other states. This indeed helps to account for the character of much of the campaigning in the Thirty Years’War, in particular what might appear a disjointed series of marches in which rival forces sometimes confronted each other. There was insufficient manpower for a war of fronts in Germany or Italy, and maps in historical atlases that suggest otherwise are misleading. Indeed, the absence of fronts helped confer additional importance on fortresses.
In addition, the political-military nature of the war itself was in part set by the problem dissected by Parrott. The availability of only one really effective field army ensured that it was necessary for powers to fight one opponent at a time, or to accept that successful offensive operations could only be mounted against one opponent. This encouraged a military diplomacy in which peace, truce, or stasis with one rival was sought so that another could be attacked. The 1629 agreement between Sweden and Poland was a good instance of this. Similarly, Spanish involvement in the War of the Mantuan Succession left the Army of Flanders short of funds and therefore with its operational effectiveness compromised, and the army downright mutinous.
The need to focus on one opponent established an important constraint on military capability and effectiveness. In so far as the categories are helpful, it had both a political and a military dimension, as the range of factors summarised under the term resources can be seen in both these lights. For example, there was the issue not only of the availability of money but also of experienced troops.
As a reminder of the interlocking nature of military struggles, and thus of the role of politics, the Habsburgs were militarily successful in northern Italy in 1630, taking Mantua and, under Spinola, pressing Casale hard, while the French relief operation languished. However, Ferdinand II withdrew from the conflict in response to the Swedish invasion of northern Germany and the problems for Imperial preparedness in the Empire created by the dismissal of Wallenstein in response to pressure from the Imperial Diet. This weakened Spanish resolve, as did the death of Spinola, leading to talks with France. As a consequence, the French were able to relieve Casale in October 1630, forcing a negotiation which finally hardened into the two treaties of Cherasco in the spring of 1631 that brought the war in northern Italy to a close.
The Spaniards conducted a successful military campaign in the early 1620s. In 1620 they helped the imperial troops to defeat the Bohemian rebels at the battle of White Mountain. Similarly, spectacular victories were achieved in 1625, enabled financially by a particularly remarkable delivery of bullion from the Americas in the previous year, like the rendition of Breda in the Low Countries, the recapture of Bahia in Brazil from the hands of the Dutch, the repulsion of the British fleet in Cadiz, and the repulsion of a French invasion in the Valtelline. However, things took a turn for the worse during the years 1627-29 with the Spanish intervention in the duchy of Mantua – a decision that bore destructive results. With the death of the childless duke of Mantua, the best prospect of succeeding him went to the French claimant, the duke of Nevers. Fearing the strategic compromise of Spanish interests in northern Italy, Olivares sent the governor of Milan to occupy the Monferrat, a Mantuan region bordering Milan to the west. In reaction, a French army was sent to the occupied region, resulting in a long and inconclusive war that lasted until April 1631. Olivares’ expectations of a short campaign were thus shattered, leaving Spain in greater financial ruin as the crown’s share of the Indies bullion went to finance the Italian front.
The Spaniards received a brief boost in confidence as the French were forced to pull forces from various fronts following internal rebellions. Similarly, the death of France’s allies in northern Italy, the Mantuan and Savoiard rulers in 1637, in tandem with the Spanish seizure of the Valtelline, marked the breakdown of French aspirations in Italy. Consequently, Richelieu proposed a truce with Spain, which was rejected by Olivares, who felt that the French proposal came from a deep weakness that could be exploited to achieve a convincing victory.
At the same time as fighting within the country itself, France became caught up in a conflict against Spain in Italy. War had not yet been declared, there were no actual battles; instead historians have spoken of a `covert war’. Richelieu believed that Italy was the `very heart of the world’ and that it was also the weak point in the Spanish empire.
The Mantuan succession proved him right. The duke of Mantua, from the House of Gonzague, died with no direct descendants but he had a cousin, another Gonzague, the duc de Nevers who lived in France and was considered a subject of the king of France. The emperor, as sovereign of Mantua, refused Nevers the right to inherit the duchy but Nevers took it anyway. As the king of France was, at that time, busy with the siege of La Rochelle, Spain thought it would be possible to chase out the French intruder although two main towns remained loyal to him, Casale Monferrato defended by a French garrison, and Mantua itself. This was a major challenge for Spain. Casale controlled the road from Genoa to Milan and Mantua was on the only road between the Milan area and the Republic of Venice, as well as standing on the road to the Brenner Pass and Austria. The duke of Savoy (who also owned the Piedmont) took up arms with the Spanish after they promised him the Monferrat area. Olivares gave the order to besiege Casale. France and Spain were on the brink of war, drawn in by minor powers.
After the capitulation of La Rochelle, Richelieu advised intervention in northern Italy in December 1628. The French supporters of an alliance with Spain were, of course, hostile to the idea, behind Marie de Medici and the Keeper of the Seals, Marillac. In their opinion, the Casale business was a minor affair and not worth the sacrifice of the efforts at reform within the kingdom and the Catholic reconquest of Europe. According to them, Richelieu was recommending war to make himself irreplaceable in the king’s eyes. Meanwhile, the policy burdened the people with higher taxes and led to general discontent. French troops crossed the Alps. Spain obtained assistance from the emperor who, as a result, had to draw troops away from the other fronts, seriously weakening them. This was the first time since 1527 that a German army had entered the Italian Peninsula. Cardinal de Richelieu, in a note to the king dated 13 January 1629, set out the salient points of a political programme: `France should think only of fortifications within its borders. It should build and open doorways allowing it access to all the neighbouring States so that it can guarantee them against oppression by Spain when the occasions arise.’ The French forces captured the redoubtable fortress of Pignerol in the Piedmont on 22 March 1630. As to the imperial army, it took Mantua in July 1630 and sacked the town.
The situation in northern Italy was linked to the situation of the Holy Roman Empire and the Hapsburgs’ ambitions were of concern to the whole of Europe. France and England favoured agreement between the two princes of the House of Vasa – the Roman Catholic King Sigismond III of Poland, and his Lutheran cousin, King Gustav Adolph of Sweden. The latter now had a free hand. He could intervene in northern Germany and provide backup for the Protestant princes who had been dispossessed by the emperor. A meeting of Electors was held in Regensburg in the summer of 1630. Father Joseph, Richelieu’s right-hand man, encouraged the German princes to refuse the election of Ferdinand II’s son as King of the Romans: that would have ensured he succeeded his father automatically, without an election, and would possibly have been one step towards the hereditary transmission of the imperial crown in the House of Hapsburg. Everything might go a different way, however. Gustav Adolph of Sweden landed in northern Germany in 1630, on the grounds that he was defending Protestantism.
When the imperial army captured Mantua, French negotiators took fright and agreed, on 13 October 1630, to sign a treaty that required the French and imperial troops to pull out of northern Italy. The situation in France was then very tense because, at the end of summer, Louis XIII had fallen seriously ill in Lyon and seemed likely to die soon. He had hardly recovered when he received news of the Treaty of Regensburg. Its ratification would mean the failure of Richelieu’s policy since France would then abandon its allies and leave the way free for the emperor. The cardinal advised Louis XIII not to ratify the treaty, claiming that the French envoys had overstepped their brief.
The rejection of the Treaty of Regensburg led to lively controversy in France; Richelieu was immediately subjected to attacks by supporters of peace and by his political adversaries who feared a war against the Hapsburgs. The Queen Mother, Marie, launched an offensive against Richelieu who believed himself to be disgraced. This was the `great storm’ or the `Day of Dupes’ of 11 November 1630 when, in fact, Louis XIII asked his minister to continue `steering the ship’ and exiled his enemies. In France, Richelieu’s political victory was greeted as a victory for `good Frenchmen’ and a defeat for the pro-Spanish faction. Soon, Queen Marie found herself on the road to exile.
In Italy, while the French and Spanish forces were about to do battle at Casale, a papal envoy called Mazarin miraculously obtained a ceasefire on 26 October 1630. The negotiations at Cherasco then led to treaties that appeared to be favourable to France with Savoy giving it Pignerol in 1632. Thanks to this, Louis XIII obtained a `gateway’ halfway between Briançon and Turin, a gateway which, in those days, was seen as the entrance to Italy and a means of rapid intervention. In the end, the Spanish government felt it had been duped by this treaty, with the complicity of the negotiator, Mazarin.