Napoleon Targets Portugal – The Prelude to the Invasion (1807)

Following the Treaties of Tilsit (July 1807), which ended the War of the Fourth Coalition, Napoleon turned his attention to Portugal, frustrated by its continued economic and military ties to Britain.

Reasons for Napoleon’s Hostility Toward Portugal

1. Portugal was Britain’s oldest ally in Europe, maintaining diplomatic and economic relations despite Napoleon’s demands.
2. British trade with Brazil was expanding, helping Britain offset the economic impact of the Continental System.
3. The Royal Navy frequently used Lisbon’s port, making Portugal a strategic asset for British naval operations.
4. Napoleon sought to seize Portugal’s navy, bolstering French maritime strength.
5. Prince Regent João of Braganza (ruling for Queen Maria I) refused to fully comply with the Continental System, keeping British trade open.
6. The conquest of Portugal would serve as a stepping stone for Napoleon’s intervention in Spain, where he sought to extend French control.

Napoleon’s Ultimatum to Portugal (July–September 1807)

• On July 19, 1807, Napoleon ordered his Portuguese ambassador to deliver an ultimatum:

  Portugal must close its ports to Britain by September 1, or face invasion.

• On August 2, Napoleon formally created the 1st Corps of the Gironde Army of Observation, placing General Jean-Andoche Junot in command.
• Shortly after, Portugal’s shipping in French ports was placed under embargo, signaling economic retaliation.
• On September 23, Napoleon publicly threatened to depose the Braganza dynasty, directly warning the Portuguese minister in France.

The Road to Invasion

Despite French pressure, Portugal hesitated, attempting to balance its long-standing alliance with Britain while avoiding war with France. However, Napoleon had already decided on conquest, viewing Portugal as an easy target that would serve as a gateway to military intervention in Spain.

Within weeks, his army would cross into Iberia, setting in motion the invasion of Portugal (November 1807) and the beginning of the Peninsular War.