Federico II Gonzaga, a son of his predecessor Francesco II Gonzaga, Marquess of Mantua and Isabella d'Este.

had been crowned Marquess of Mantua in April 3, 1519, initially under the regency of his mother and his uncles Sigismondo and Giovanni Gonzaga.

He receives the imperial investiture from emperor Charles V on April 7, 1521.

Despite his poor military experience, Pope Leo X names him Gonfalonier and Captain General of the Church (commander in chief of the Papal Army), though a clause allows Frederick to avoid fighting against the Empire, to which Mantua has always traditionally been an ally.

Holy Roman Emperor Charles V and Pope Leo X, at the start of the Italian War in 1521, move jointly against the Duchy of Milan, the principal French possession in Lombardy.

A large Papal force under Federico II Gonzaga, Marquis of Mantua, together with Spanish troops from Naples and some smaller Italian contingents, concentrates near Mantua.

The German forces that Charles sends south to aid this venture pass through Venetian territory near Vallegio unmolested; the combined Papal, Spanish, and Imperial army then proceeds into French territory under the command of Prospero Colonna.

The Emperor, simultaneously with his promulgation of the Edict of Worms against Martin Luther, promises the Pope the restoration of Parma and Piacenza to the Medici and of Milan to the Sforza.

Leo, needing the Imperial mandate for his campaign against what he views as a dangerous heresy, promises to assist in expelling the French from Lombardy, leaving Francis with only the Republic of Venice for an ally.

Imperial Invasion of Northern France: Henry of Nassau's Campaign (June 1521)

In June 1521, amid rising tensions marking the renewal of conflict between Francis I of France and Emperor Charles V, imperial armies under the command of Henry of Nassau launch an aggressive invasion into northern France, opening a decisive phase of the Italian War of 1521–1526.

The invading Imperial forces devastate strategically important French frontier towns, including Ardres and ...

...Mouzon, both razed to the ground. Subsequently, ...

...they lay siege to Tournai, which had been returned to French rule only recently in 1518, following brief English occupation after the Battle of the Spurs (1513). The choice to attack these particular cities demonstrates clear Imperial intent: Ardres holds symbolic importance as the site near the recent diplomatic pageantry of the Field of the Cloth of Gold (1520), while Tournai is a critical economic and military stronghold.

This northern invasion, initiated by Henry of Nassau, aligns strategically with Emperor Charles V's broader geopolitical ambition of weakening French influence in the Low Countries and asserting dominance along the Franco-Imperial frontier. The incursion exposes France's vulnerability in its northern territories, places substantial pressure on Francis I, and contributes significantly to destabilizing the fragile peace of Western Europe.

The immediate consequence of this invasion is a marked escalation of hostilities between Charles V and Francis I, drawing England deeper into continental affairs, as Henry VIII increasingly aligns with Imperial interests against France. Over the longer term, this aggressive opening sets the stage for further Imperial-French confrontations, prolonging and intensifying the Italian Wars, deeply influencing the geopolitical balance of Atlantic West Europe throughout the early sixteenth century.

Siege of Mézières: Imperial Advance Halted by Bayard and Montmorency (1521)

In 1521, as part of the escalating hostilities marking the Italian War of 1521–1526, an Imperial army commanded by the prominent military leader Franz von Sickingen advances aggressively into Picardy, targeting the critical fortress city of Mézières (now part of Charleville-Mézières). Sickingen's campaign aims to penetrate deep into northern France, exert pressure on King Francis I, and further destabilize the French frontier.

However, the Imperial forces meet unexpectedly fierce resistance at Mézières. The city's defense is led by the legendary knight, Pierre Terrail, Seigneur de Bayard, famed throughout Europe as the embodiment of chivalric virtue, and by the rising military commander Anne de Montmorency, who later emerges as a leading French statesman. Despite intense bombardments and sustained assaults, the French defenders stubbornly hold their ground, repelling each Imperial attempt to breach the city's walls.

The successful defense of Mézières has important strategic and symbolic consequences. Forced to withdraw by the determined resistance, Sickingen's troops retreat, leaving behind a significant Imperial setback. This defensive victory buys critical time for Francis I, allowing the king to assemble and mobilize French forces capable of effectively countering the Imperial invasion.

The siege’s significance extends beyond the immediate military outcome. By successfully resisting Imperial aggression, Bayard and Montmorency bolster the French morale at a precarious moment and reaffirm the resilience of the French frontier. For Montmorency, his prominent role in the defense solidifies his reputation, launching him into a prominent military and political career. For Bayard, already renowned for his valor, this defense further cements his legendary status.

In a broader context, the failure at Mézières disrupts Imperial momentum, preventing Emperor Charles V from exploiting initial gains in Picardy. This turning point thus shapes the ensuing phase of the war, confirming the French capacity for sustained resistance despite intense military pressure.

The Missed Opportunity at Valenciennes: Francis I Hesitates Before Charles V (1521)

On October 22, 1521, during the critical early phase of the Italian War of 1521–1526, King Francis I of France and Holy Roman Emperor Charles V come face to face near the strategic city of Valenciennes. The encounter offers Francis a potentially decisive opportunity to strike directly at the main Imperial army and possibly capture or decisively defeat Charles himself.

The French army, numerically strong and eager for battle, includes prominent commanders such as Charles III, Duke of Bourbon, who passionately urges immediate action. However, despite Bourbon's counsel, Francis hesitates—possibly uncertain about the enemy's precise strength or wary of the potential risks of a major engagement. This hesitation proves critical: it allows Charles V to reassess his position and promptly begin a strategic retreat.

By the time Francis resolves to attack, heavy seasonal rains begin, severely hampering French mobility and undermining any effective pursuit of the retreating Imperial forces. Thus, Charles V successfully extricates his army from a perilous situation without a significant battle.

Francis's hesitation at Valenciennes is widely viewed by contemporaries and historians alike as a crucial missed opportunity. Had he engaged promptly, Francis might have delivered a decisive blow to Charles V's forces, potentially altering the war’s trajectory. Instead, the failure to engage reinforces Imperial morale, solidifies Charles’s cautious strategy, and undercuts Bourbon’s trust in the French King's military judgment—factors that will significantly impact the political and military developments of the ensuing years.

French-Navarrese Capture of Fuenterrabía (October 1521): A Strategic Victory in the Franco-Spanish War

In late October 1521, French-Navarrese forces under Admiral Guillaume Gouffier, Lord of Bonnivet, and Claude of Lorraine successfully seized Fuenterrabía (Hondarribia), a key fortress town at the mouth of the Bidasoa River, on the Franco-Spanish border. This marked a significant strategic victory for France and Navarre in their war against Emperor Charles V and provided a foothold in northern Spain that would remain in French hands for the next two years.

Strategic Importance of Fuenterrabía

• Fuenterrabía controlled the Bidasoa River, which formed a natural border between France and Spain, making it a critical military and trade route.
• The town was heavily fortified, and its capture opened a direct path into Castile for future French incursions.
• The French saw Fuenterrabía as a potential base for further efforts to reclaim Navarre and challenge Spanish dominance in the region.

The French-Navarrese Offensive and Capture of Fuenterrabía

• After the defeat of the Navarrese-French army at the Battle of Noáin (June 30, 1521), King Henry II of Navarre and his allies shifted focus to border strongholds.
• French forces under Bonnivet and Claude of Lorraine maneuvered extensively before launching a successful attack on Fuenterrabía in October 1521.
• The siege and subsequent capture of the city provided France with an advantageous position for the next phase of the conflict.

Consequences of the French-Navarrese Victory

1. A New Front Against Spain

   • Holding Fuenterrabía gave the French a launching point for future offensives into Spain.
   • It forced Charles V to devote more troops to defending the border, stretching Spanish military resources.

2. Prolonged French Occupation (1521–1524)

   • The French held Fuenterrabía for two years, making it one of their longest-lasting territorial gains in the conflict.
   • However, Spanish forces constantly harassed the French garrison, leading to continued instability in the region.

3. Symbolic and Political Impact

   • The capture of Fuenterrabía boosted morale for Navarrese loyalists in exile, keeping hopes alive for the eventual reconquest of Navarre.
   • It also weakened Charles V’s hold over northern Spain, forcing the Habsburgs to commit additional troops to Iberia.

Conclusion: A Temporary but Significant French Victory

The capture of Fuenterrabía in October 1521 was one of the most notable successes of the French-Navarrese alliance against Charles V. Although not enough to restore Navarre, it gave France a strategic foothold in Spainthat would remain in their hands until 1524, when Charles V’s forces would finally retake the city. This event underscored the continued struggle for control over the Pyrenean frontier and the ongoing tensions between France and Spain over Navarre.

Colonna has for the past several months fought an evasive war of maneuver against Odet de Foix, Vicomte de Lautrec, the French commander, besieging cities but refusing to give battle.

The French situation has deteriorated considerably by November.

Odet de Foix, Vicomte de Lautrec, the French governor of Milan, has been tasked with resisting the Imperial and Papal forces; he is outmatched by Prospero Colonna, however, and by late November has been forced out of Milan and has retreated to ...