The San Ju
The Transit Campaign (1856-1857), item by item
The San Juan River was not only a natural frontier: it was the decisive scenario where Costa Rica’s survival against William Walker’s filibuster project was defined.
Between late 1856 and early 1857, Major Máximo Blanco Rodríguez led some two hundred Costa Rican soldiers along this strategic river corridor, from the interior of the country to the Caribbean, capturing steamships, forts and controlling the inter-oceanic route.
This map traces, from left to right (west to east), the key points of this forgotten campaign .
📍 Origin of the expedition: the interior of Costa Rica
San José → San Carlos Pier
The feat did not begin on the river, but on land.
From San José, the Vanguard Column undertook a grueling march to Muelle San Carlos, on the upper reaches of the San Carlos River, a tributary of the San Juan.
This overland journey marked the beginning of an extreme logistical operation, carried out without naval support, without sufficient resources and in adverse weather conditions.
📍 Entrance to the river theater
Boca del Rio San Carlos
At the confluence of the San Carlos River with the San Juan River, the Costa Ricans first entered the center stage of river warfare.
Here the first indirect contact with filibustering forces occurred, and the advance eastward downstream began.
📍 First strategic points of the middle river.
Old Castle
Former Spanish colonial fort, deteriorated but still symbolic.
Its capture allowed the Costa Ricans to consolidate their presence in the middle stretch of the river and to prepare operations of deception and capture of enemy steamers.
Raudal del Toro
Area of dangerous rapids, key to river ambushes.
Naval deception operations took place here, including the famous curtain maneuver on the steamer Bulwer, which allowed captures without firing a shot.
Machuca
Critical river crossing, used by filibuster steamers to transport troops and supplies.
Its control reduced enemy mobility upriver.
📍 Influents and logistical control
San Carlos River
Fundamental tributary for the connection with the Costa Rican interior.
Guaranteed human and material supply from the Central Valley.
Colpachí Estuary
Swampy area near the delta, used as a secondary road and natural refuge.
Important for discreet operations and concealed movements.
Sarapiqui River
Although not directly part of the San Juan, it was key as an alternative transit route and logistical support.
It connected the interior with the Caribbean and reinforced Costa Rican pressure on the Transit Route.
📍 The heart of the campaign.
La Trinidad
This was the nerve center of the campaign.
This is where the first direct confrontation with the filibusters took place and the main Costa Rican camp was established.
From La Trinidad, the capture of steamers was coordinated, troops were reorganized and constant pressure was maintained on enemy logistics.
It is also the place to which Máximo Blanco was forced to return, by order of General José Joaquín Mora, once the capture of the fort upriver was consolidated.
📍 The Caribbean and the Transit Route
Greytown / San Juan del Norte
Caribbean port and eastern end of the river.
Here the first filibuster steamers were captured, interrupting the Transit Route that connected the Atlantic with the Pacific and sustained William Walker’s power.
The control of Greytown meant the logistical collapse of filibustering in Nicaragua.
📍 The decisive move upstream.
Fort San Carlos
Located at the outlet of the river from Lake Nicaragua, it was the most strategic point of the entire river system.
After capturing steamers in the Caribbean, the Costa Rican forces sailed upstream against the current to take the fort.
At the end of 1856 and beginning of 1857, Fort San Carlos passed into Costa Rican hands, sealing the total control of the San Juan River.
This was the highlight of the campaign.
Strategic epilogue – The decision to survive
After securing the Fort of San Carlos in late 1856 and early 1857 -consolidating Costa Rican control of the upper San Juan River- Major Máximo Blanco Rodríguez was not “forced to withdraw” from the campaign, as later simplified in some accounts.
On the contrary, it received the order to cover again La Trinidad, a neuralgic and exposed point of the fluvial line, but without the minimum necessary resources to sustain that position. From San José, the political power celebrated the successes of the Vanguard Column and capitalized on its victories, but did not send sufficient reinforcements, food or ammunition, nor did it guarantee a basic logistic chain for the survival of the men stationed on the river.
In La Trinidad, Blanco and his little more than two hundred soldiers were isolated, sick, poorly fed and with increasingly precarious weaponry. Faced with the evidence that the permanence meant the silent annihilation of his troops – not by the enemy, but by abandonment – Máximo Blanco made an extreme but responsible decision: to abandon the position as an act of collective survival, prioritizing the lives of his men over blind obedience to impossible orders.
This decision, taken under extreme conditions, would mark the beginning of Blanco’s political and symbolic displacement within the official narrative. While San José continued celebrating the captures of steamers and the strategic achievements of the Transit Campaign, the commander who had made them possible was progressively unprotected, isolated and, finally, silenced.
It was not a military retreat.
It was the price of having won too far from the center of power.
