Military Subjects: Battles & Campaigns

River Crossings in the Peninsular War

By Richard Tennant

The essence of the defence of Portugal is the box created by its rivers.

The River Duero flows west into the Atlantic at Porto, some 300 km north of Lisbon and the estuary of the River Tagus. The valley of the Duero is largely in the form of a canyon within Portugal and then for 112 km. the river forms part of the national border line between Spain and Portugal, in a region of narrow canyons which formed a historical barrier to invasions. After the destruction of the bridge-of-boats at Porto in 1809 the only available crossings were by ferries.

The rivers Coa and Agueda are about 200 kilometres to the east from the coast, forming the Portuguese/Spanish border, both running almost due north into the Duero. Whilst the lower reaches of the Coa and Agueda have carved canyons into the countryside, the upper reaches had a few bridges and several fords. The upper reaches therefore did not form any substantial barrier, but rather a demarcation of the natural border between the two countries.

The Tagus is the longest river in Spain, rising some 240 km east of Madrid; at its mouth at Lisbon it is over 20 km wide. Bridges linking the country north and south of the river were few and far between; there were regular ferry stations and a few fords which could be usable only in high-summer. The need for good north / south communications had been recognised back in Roman times and the first permanent bridge up the river was constructed just over the Spanish side of the border at Alcantara by order of the Spanish-born Emperor Trajan in 98 AD.

The easy by which large military forces could move up and down the Portuguese/Spanish border had always had a significant impact on the strategic restraints imposed on, or the flexibility available to, the contesting generals.

In the recording of the history of the Peninsular War many river crossings are mentioned but there has been little written about technicalities of the bridges or the fords themselves. This series of papers is intended to examine these in some detail and describe a few of the anomalies.

 

Placed on the Napoleon Series: March 2019



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