1. Spread of Nationalism and Guerrilla Warfare: The invasion of Portugal and subsequent occupation of much of Spain triggered a strong sense of national identity and resistance among the Iberian people. This led to the emergence of guerrilla warfare tactics, as ordinary citizens, peasants, and local forces engaged in hit-and-run attacks against French troops. These guerrilla actions made it difficult for Napoleon's forces to control the territory and tied up significant military resources.
2. Increased British Involvement: The British viewed Napoleon's presence in the Iberian Peninsula as a strategic threat to their interests and used the Portuguese as an ally to fight the French. The long-term commitment of British troops and financial support to the war in Spain and Portugal helped maintain an active front against Napoleon's empire. The Duke of Wellington's brilliant leadership and the tenacity of the Anglo-Portuguese forces proved instrumental in turning the tide against the French.
3. Financial and Economic Strain: The Peninsular War was an extremely costly undertaking for France. The need to station large armies in hostile territories, coupled with the disruption of trade routes and the guerrilla activities, put a significant strain on the French economy. This was compounded by the fact that the British controlled the seas, making it challenging for France to resupply its troops and obtain necessary resources.
4. Typhus Epidemic: The war in the Iberian Peninsula also coincided with a devastating typhus epidemic that ravaged both the French and Spanish armies. The disease decimated troop strength, weakening Napoleon's forces and further compounding the difficulties he faced in maintaining control of the region.
5. Growing Opposition within France: The increasing casualties, financial burdens, and protracted nature of the Peninsular War led to growing dissatisfaction and discontent within France itself. Anti-war sentiment gained traction, andNapoleon's government faced increasing pressure to end the costly conflict. This internal unrest further weakened the stability and popularity of his regime.
6. Overextended Empire: The Peninsular War diverted Napoleon's attention and resources away from other fronts, such as the looming conflict with Russia. The attempt to maintain control over the vast territories of his empire, while engaging in a protracted and draining conflict in Spain, placed a significant strain on his military capabilities and strategic decision-making.
In conclusion, while the Peninsular War brought initial victories and secured Napoleon's control over much of the Iberian Peninsula, it proved to be a strategic blunder that contributed significantly to his eventual downfall. The combination of fierce resistance, guerrilla tactics, British involvement, financial strain, disease outbreaks, and growing internal opposition eroded his power, making him more vulnerable to defeat in future campaigns and ultimately leading to his abdication in 1814.