The Passage of Humaitá (Portuguese: Passagem de Humaitá) was an operation of riverine warfare during the Paraguayan War − the most lethal in South American history − in which a force of six Imperial Brazilian Navy armoured vessels was ordered to dash past under the guns of the Paraguayan fortress of Humaitá. Some competent neutral observers had considered that the feat was very nearly impossible.
The purpose of the exercise was to stop the Paraguayans resupplying the fortress by river, and to provide the Empire of Brazil and its Allies with a much-needed propaganda victory. The attempt took place on 19 February 1868 and was successful – the attackers had hit upon the fortress' weakness. It restored the reputation of the Brazilian navy and the Brazilian Empire's financial credit, and caused the Paraguayans to evacuate their capital Asunción. Some authors have considered that it was the turning point or culminating event of the war. The fortress, by then fully surrounded by Allied forces on land or blockaded by water, was captured on 25 July 1868.
Historical background The Fortress of Humaitá was a defensive system on a bend in the River Paraguay, not far from its mouth. Long considered to be almost impregnable,See the main article Fortress of Humaitá. it prevented enemy shipping ascending the river and hence invading the Republic of Paraguay. There may have been other routes by which the country could have been invaded, but they were considered more difficult still. From the main article on the Fortress of Humaitá it appears that Marshal-President López of Paraguay may have calculated that, because the fortress could not be bypassed except at ruinous expense, he could risk making war on the much more populous Brazil and Argentina.
The Paraguayan War (also known as the War of the Triple Alliance) of 1864–1870 was the most lethal in South American history, and − in terms of its relative mortalityI.e. the overall death rate, civilian plus military. − very possibly the worst in modern history, anywhere. It actually commenced when López seized the Brazilian ship Marques de OlindaOn 12 November 1864 (Plá, 222). on her routine voyage up the River Paraguay to the Brazilian province of Mato Grosso,At that time the province of Mato Grosso comprised the current Brazilian states of Mato Grosso and Mato Grosso do Sul. The latter only became a state in 1977 after being dismembered from Mato Grosso. then sent military forces to invade the province itself. It developed further when he seized Argentine naval vessels moored in the port of Corrientes, north east Argentina.On 13 April 1965 (Plá, 222). Thereafter López sent two further armies, one to invade the Argentine province of Corrientes along the River Paraná and the other to invade the Brazilian province of Rio Grande do Sul along the River Uruguay. On 1 May 1865 Brazil, Argentina and Uruguay signed the Treaty of the Triple Alliance by which they would not negotiate peace with ParaguayExcept by the unanimous consent of all three allies. until the government of López had been deposed.Treaty of the Triple Alliance, article VI.
Further, for Brazil the river was the only practicable route to its interior province of Mato Grosso, which had been invaded by the forces of López earlier in the War. The war aims of the Allies (Brazil, Argentina and Uruguay) explicitly included the capture and destruction of Humaitá,Treaty of the Triple Alliance of 1 May 1965, Protocol, article 1. and it was the prime military objective of the Allied high command.On the same day that the Treaty was signed (1 May 1865) the Allied high command agreed a strategic plan. Its first point was that Humaitá was their primary strategic objective to which all others must be subordinated: Tasso Fragoso, II, 33.
The Allies' strategic problem
It took the Allies about a year to defeat the invading Paraguayan forces in the Brazilian province of Rio Grande do Sul and expel them from Argentina. According to their treaty they now had to neutralise Humaitá and depose López. In April 1866 the Allies crossed the River Paraná into southwestern Paraguay, occupying a small strip of territory. Their next strategic problem was how to proceed up the River Paraguay, getting past the Fortress of Humaitá.
Briefly, the fortress of Humaitá was built on a sharp concave bend in the river and comprised more than a mile of heavy artillery batteries atop a low cliff. The channel was only 200 yards wide, and ran within easy range of the batteries; a heavy chain boom could be raised to block the navigation and detain the shipping under the guns. 'Torpedoes' (improvised contact naval mines) could be released or anchored in the stream. On its landward side the fortress was protected either by impassable terrain or by 8 miles of trenches with 120 heavy guns and a garrison of 18,000 men. An attempt to capture one of its outworks by frontal attack failed disastrously at the Battle of Curupayty (22 September 1866); another frontal attack was out of the question.In April 1867 the Brazilian commander Caxias admitted that a frontal attack would be the act of a "madman" and lead to "certain defeat" (Tasso Fragoso, 235).Much later, on 16 July 1868, when Caxias thought the Paraguayan garrison was abandoning Humaitá, a frontal attack was attempted by Osorio. It was repelled with considerable loss: Doratioto, 313-4.
From a naval perspective the heavy guns of the fortress might – in principle – be bypassed by the latest ironclads (armoured vessels), provided the chain boom could be cut and any 'torpedoes' avoided. But those vessels could not have operated ahead of their forward bases for long, because they would need to be resupplied with fuel, ammunition and provisions. Furthermore, the Brazilian navy command claimed there was no room inside the ironclads for the conveyance of troops; the wooden transport vessels could not have accompanied them.
The land operation in which the Allied land forces did succeed in capturing the Humaitá complex, known as the Siege of Humaitá, is outside the scope of this Article. However, to starve out Humaitá it was necessary to stop the Paraguayans resupplying it by river. But, in order to do that, it was necessary to obtain command of the river, in other words, to steam past Humaitá.
Difficulties facing the Allies
1. The home front By the end of 1867 the Allies were badly in need of a propaganda victory. The war had cost them a lot of menAccording to Schneider the number of men killed, wounded and "lost" (deserted or taken prisoner) was 18,408, of which about four thousand were killed outright. However another 10,000 were killed by cholera and other diseases: Burton, 303. and money; though they still had superior manpower yet they were stuck in the small area of southwestern Paraguay shown in the map. The disaster of Curupayty had sunk their morale and led to a year's inactivity. And it had fostered an already strong anti-war faction in Argentina. Armed revolutions had broken out in that country – especially in the Andean provinces – demanding peace with Paraguay. It had got to the point that the Allied commander-in-chief General Bartolomé Mitre had temporarily quit ParaguayOn 9 February 1867 (Ouro Preto, 288). with 4,000 Argentine troops in order to put down the revolts, leaving the Brazilian General the Marquis of Caxias in charge.Mitre returned on 8 August (Ouro Preto, 298).
Brazil financed its warlike operations partly by borrowing in the financial markets especially the City of London, and advanced money to Argentina and Uruguay. The lack of progress in the war was affecting its financial credit.
In June 1867 Caxias wrote to a colleague: My friend, let us see if we can conclude this cursed war which has ruined our country, and whose duration shames us.Caxias to Osorio, 6 June 1867. (Wikipedia translation.).
2. Extended lines of communication
Lengthy lines of communication vastly increased the difficulty and cost of the war for Brazil. According to the American envoy to Paraguay, López had banked on that fact when deciding to make war on the Brazilian Empire in the first place.
Steam vessels were the only practicable means of communication. Thus in Brazil the overland journey from São Paulo to Mato Grosso took two and a half months by fast mule; by steamship, although the detour south through the River Plate and up through the River Paraguay was vast, it could be done in little over a fortnight.It continued to be the only practicable route until 1910, when a railway was at last built from São Paulo to Cuiabá: Doratioto, 26. Tension over this route had been one of the causes of the Paraguayan war.
Ammunition or other stores shipped from Rio de Janeiro, Brazil to the naval arsenal at Isla del Cerrito, near the mouth of the river Paraguay, had to travel an extensive water route.
LegRoute afterwards streamlined by the Brazilian minister of marine: Ouro Preto, 123-3. Water routeNautical milesAccording to the tool MarineTraffic Voyage Planner. Kilometres Rio de Janeiro (Brazil) to Montevideo (Uruguay)South Atlantic Ocean 1099 2036Montevideo (Uruguay) to Corrientes (NE Argentina)River Plate – Paraná delta – River Paraná 6511206Corrientes (NE Argentina) to vicinity of Humaitá (Paraguay) River Paraná – River Paraguay1426
Vessels requiring to be repaired could not be sent down to Buenos Aires for lack of facilities, and Rio de Janeiro was too far. Isla del Cerrito ("island of the hillock") was and is a small island at the confluence of the Paraná and Paraguay rivers. There the navy established a machine shop employing 20 men; a boatyard manned by 50 carpenters, etc; a coal bunker; a gunpowder mill; a naval hospital; and even a church. Good naval timber required for repairs was harvested locally.
Because the river was blocked at Humaitá, stores required further north had to go by oxcart convoys on a route flanking Humaitá to the east. Those convoys were the object of repeated Paraguayan ambushes.
3. Inherent difficulty in effecting the naval passage of Humaitá Although some foreign observers were critical of the Brazilian navy's lack of zeal and implied that it should have forced the passage long ago, those observers were not naval men. One who was, Commander KennedyHowever Commander Kennedy, who only visited the scene after the event, made no secret of his admiration for Vice-Admiral Inácio, writing: "The energetic proceedings of Admiral Ignacio, and the gallantry displayed by the fleet, had been the theme of universal admiration" (Kennedy, 144). ("Energetic proceedings" is contradicted by several other sources mentioned in this Article.). of the Royal Navy, wrote that there were real difficulties, which he identified as these:
The river approach to Humaitá – which included the heavily armed preliminary fortifications at Curupayty – was shallow, narrow, and uncharted. It lent itself to the release of "torpedoes" (improvised contact naval mines). It was too shallow for the heaviest ironclad vessels, except during the river's seasonal rise.Seasonal tropical rainfall in the Upper Paraguay basin causes the river to rise. Because the river discharges into the Paraná river (which itself rises or falls according to the rainfall in its own headwaters) there may be backing up, and the pattern is not entirely predictable: Burton, 295; Johnston, 498. The seasonal difference between high and low water could be as much as . But if these vessels did proceed at high water, they might be grounded, or trapped (neither able to advance or retreat), when the waters fell again. Commander Kennedy's evaluation: It is difficult to conceive a more formidable obstacle to an advancing squadron than this small portion of the river between Tres Bocas and Humaitá.