page_title: Passage of Humaitá
section_title: The chain boom of Humaitá deters Inácio
hierarchical_section_title: Passage of Humaitá / The chain boom of Humaitá deters Inácio
caption_attribution_description: English: Humaitá in late 1867 with the ironclads trapped above Curupaty.
context_page_description: The Passage of Humaitá was an operation of riverine warfare during the Paraguayan War − the most lethal in South American history − in which a force of six 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' Achilles heel. 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.
context_section_description: Inácio sent Barroso upriver to reconnoitre Humaitá; she reported that the river was indeed blocked by a boom of three parallel chains floating on pontoons. The tactical problem now was how to get past the chain boom.
  There was some military knowhow about this.  According to a professional paper published some years before by the Corps of Royal Engineers in Dublin a heavy steamship could snap almost any chain provided it was moving fast enough; for this reason it was prudent for the defenders to provide three chains − breaking the first reduced the ship's velocity. The paper said that a 1,000 ton ship steaming at 15 knots could snap a chain of 2.5-inch round iron links.  The chain link diameter at Humaitá was not known to the attackers; the largest ironclad (Brasil) was 1,500 tons but her top speed was only 11.3 knots; she would be steaming against an adverse current of up to 3 knots; and not one, but three chains were reported.
  In his memoirs the Brazilian minister of marine wrote they knew that their ships would have to proceed single file in the narrow channel: if the first failed to snap the chain it could neither back up nor turn round, nor get up enough way for a second, successful attempt at the chain.  The vessels would be trapped under the guns of Humaitá.  Further, the Brazilians feared that the Paraguayans, who were desperate to get their hands on an ironclad, might try to seize the isolated vessel by human wave boarding tactics (which, indeed, the Paraguayans tried to do more than once on later occasions).  The snapping method was not tried.
  There were alternative, if heroic, methods of severing a chain boom.  Sending out a party under the defending guns to cut it with a cold chisel was one. Seizing the chain house or blowing it up with gunpowder were others.  Both methods were urged upon the Brazilians by General Mitre but were not attempted.
  The river was falling.
  From the main article on Inácio it appears that he was prone to depression; on 30 August he sent his subordinate commanders a questionnaire as to the feasibility of passing Humaitá; the questions suggested the answers he wished to receive; for example:
  
  Finally: in the present revolutionary circumstances of the Republics of the River Plate [meaning Argentina], knowing their feelings about the Empire of Brazil, is it prudent to risk the most important part of our Navy to a certain and inevitable ruin, without being convinced that it avoids a greater evil, or gives success to our cause and triumph to our arms?
    His subordinates responded appropriately.
  Inácio informed Caxias: "I shall not risk the fleet".  On 26 August Caxias told Mitre that, shortly, the fleet would need to retire again below Curupayty; in those circumstances it would be "unpardonable recklessness" to attempt to pass Humaitá; accordingly, he intended to order it to retire to its original position.
  There followed a correspondence between Mitre and Caxias in which the nominal commander-in-chief and his nominal subordinate argued the toss in the diplomatic language of the era; Mitre reminded him of the divers occasions when (he claimed) the navy had let them down. To descend below Curupayty again would look weak, as well as exposing the ironclads to battery fire, torpedoes and the risk of seizure by boarding.  The ironclads stayed above Curupayty.
  According to George Thompson, if the ironclads had attempted to pass Humaitá at that point they would have faced only three 8-inch guns and about six 32-pounders; the other guns had been taken to reinforce Curupayty.
caption: Humaitá in late 1867 with the ironclads trapped above Curupaty.  The ironclads moored at porto Elisário and were supplied by an emergency route through the almost impassable Chaco.
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