In the years following the turn of the twentieth century, the military aircraft of the world took shape. The most famous (and the one that sparked the design of the Wright brothers flying machine) was the German Fokker D.VII, which was first used to successfully intercept British zeppelins in the skies over Germany in November of 1915, and was in action in the skies over Europe for the remainder of the year. The British Royal Flying Corps, however, had been working on their own design, which would soon become the first British designed, British built and British operated aircraft to win the skies over Europe.

In the early 1920s, land-based bombers were invented, and the airplane was no longer the exclusive domain of the navy. These new aircraft were able to carry heavy loads and large bombs over great distances, and this enabled them to perform a variety of roles, including attacks on ships in the high seas. The first attack by aircraft on land was performed by the Italian Royal Air Force on April 26, 1918, when they bombed the Austrian town of Pescara in an attempt to capture a railroad bridge. This raid resulted in only five fatalities, compared to the 30,000 deaths that the Austrians had suffered in World War I.

On November 14th, 1928, the United States Air Force’s 2nd Bomb Group, flying from a base in Rio de Janeiro, launched a mission to bomb the ocean liner SS Carmen, which the U.S. had accused of smuggling arms to enemies of the Allies in the First World War. As the bombers approached their target, the aircraft encountered fierce anti-aircraft fire from two British-built Bristol F.2B fighters. The 2nd Bomb Group’s bombers were armed with additional machine guns, and the pilots were confident that their guns would be able to shoot down the German-built airplanes. The 2nd Bomb Group’s commander, however, decided to send his planes into the fight anyway; the 2nd Bomb Group’s aircraft were

In the 1930s war between Bolivia and Paraguay, a mixed bag of aircraft acquired from the United States and Europe played a significant role.

The Chaco War, which lasted from 1932 to 1935 and involved the continent’s only landlocked republics, Bolivia and Paraguay, was the largest South American conflict of the twentieth century. While Bolivia followed a World Battle I strategy of controlled trench warfare with slow but secure marches, Paraguay fitted its limited military resources to the peculiarities of its region for a remarkable war of movement akin to Germany’s Blitzkrieg in World War II. Bolivia’s stronger air force was tasked with backing up its cautious advances, whereas Paraguayan General José Félix Estigarribia referred to his planes as “the eyes of the army,” but they were employed significantly more aggressively.

The closeness between Estigarribia and his aviators is exemplified by an anecdote from September 23, 1934. A Bolivian Curtiss-Wright CW-14R Osprey crewed by Sub Lts. Alberto Paz Soldán and Sin­ecio Moreno was chasing a Paraguayan Fiat CR.20bis flown by Captain Tomás A. Ruffinelli Jr. Ruffinelli heard gunfire and the sound of breaking glass as he checked his tail. When he turned his sight back to the front, he noticed his windscreen was filled with bullet holes. His life had been saved by that small head motion. Estigarribia approached Ruffinelli a few days later and inquired about his age. “Wrong, just two days old!” the general said when the pilot replied that he was 24.

Biplanes Battle for Supremacy in South America Two CR.20bis fighters served in the 11th Fighter Squadron, “Los Indios” (The Indians), of which two survived the war. (Photo credit: Antonio Luis Sapienza)

The Chaco Boreal, a vast flatland roughly the size of Colorado, was the disputed territory that sparked the war. Despite being covered in quebracho trees, cacti, thorn scrub, and tall grass savanna, the area is desert except during the rainy season, which turns it into a muddy swampland from November to April. Temperatures drop dramatically at night, from highs of over 100 degrees to well below freezing. As a result, airplane mechanics were compelled to empty the coolant from the radiators every afternoon during the war to prevent them from being shattered by the frozen liquid, then replenish them every morning. The constant presence of dust rendered engines unserviceable at an alarming rate. 

Despite its greenery, the Chaco has the appearance of a desert—a horrible green desert. Due to the lack of geographical features, aerial navigation was extremely difficult, and pilots frequently became disoriented when flying across the enormous area.

Since the days of the Spanish empire, Bolivia has claimed the Chaco, but it was more physically and ethnically related to Paraguay. When oil was discovered near Villa Montes, both governments moved quickly to explore and take control of the area. This resulted in the first skirmishes in 1928, which culminated in open combat four years later.

Bolivia’s air capabilities were entirely based in Villa Montes, near the Chaco border, when the conflict officially began in July 1932. Three Vickers Type 143 Bolivian Scouts, five Vickers Type 149 Vespa IIIs, and three Breguet 19A.2 two-seater army cooperation aircraft made up Bolivia’s air force at the time. With a fighter squadron and a reconnaissance-bomber squadron, they constituted the 1st Air Group, which was commanded by Major Jorge Jordán Mercado. The 1st Fighter Squadron of Paraguay had six Wibault 73C.1s and the 1st Reconnaissance and Bombing Squadron had five Potez 25A.2s, but not all of them were operational.

Biplanes Battle for Supremacy in South America The Osprey was a mainstay of the Bolivian air force, being less expensive than the Falcon and well-liked by its pilots. (Image courtesy of Historynet Archives)

Despite being slower and less nimble than their Bolivian counterparts, Paraguay’s Potez 25s survived 12 of 14 dogfights and even shot down one. Apart from the Potez’s rugged design, the defensive doctrine developed by Major Vicente Almandos Almonacd, an Argentine volunteer in the French air force during World War I who served in the Argentinian military mission in Paraguay in 1932, was the key to this. When attacked by hostile fighters, Almonacd taught his pilots to fly at treetop level and slow their speed to near stall speed, zig-zagging every 10 seconds. Faster adversary fighters would usually overtake the two-seater too quickly to aim at it with such defensive move. The pilots were also told to fly in a close V formation to cover each other’s backs and sides. As a result, a fighter attacking a formation of three or four Potez 25s from 6 o’clock would be met by machine gun fire from six to eight. The consequences could be fatal.

Boquerón, an isolated Bolivian-occupied garrison in the south-central Chaco whose entire significance resided in its water source and two rough roads going east to the Paraguay River, saw the start of the first big military operations. To bolster their onslaught, the Paraguayans relocated all of their operational aircraft—three Wibaults and five Potezes—to Isla Po, near Boquerón, in August. The Bolivian aircraft, however, remained 340 miles distant.

The first aerial action of the war occurred on September 9 when a Bolivian Vespa and two Scouts intercepted a pair of Paraguayan Potez 25s bombing Boquerón. Major Jordán’s Scouts bounced a Potez and seriously injured its pilot, 1st Lt. Emilio Rocholl. Nonetheless, Rocholl’s observer, 1st Lt. Román Garca, assumed command of the plane and flew in close formation with the other Potezes at treetop level, fending off their assailants until they returned to Isla Po. Boquerón eventually fell into Paraguayan hands, and Bolivians were forced to flee the central Chaco. 

Biplanes Battle for Supremacy in South America 1st Lt. Leandro Aponte leans against a Los Indios squadron Fiat CR.20bis. (Photo by Antonio Luis Sapienza, courtesy of Ramiro Molina Alanes)

Each of the warring countries got a new batch of warplanes in late 1932, which would dominate the Chaco skies for the remainder of the fight. The Paraguayans received eight new Potez 25 TOEs between October and December, which had larger fuel tanks and a greater range. The four remaining Wibaults were consigned to home air defense, while the three remaining Potez 25A.2s were dispatched to Asunción for repairs. In addition, Paraguay got five Fiat CR.20bis planes in January-March 1933, which formed the 11th Fighter Squadron, “Los Indios” (The Indians).

Bolivians began importing up to eight Curtiss-Wright Model 35A Hawk II fighters and 18 CW-14R Osprey fighter-bombers in December, with the latter being employed routinely, even as two-seat fighters, while the Hawks were only deployed on rare occasions. They had 12 combat planes in two squadrons in January. Bolivians began withdrawing their Scouts in July after retiring their worn-out Breguets and Vespas from frontline service in April. 

The earlier forms, on the other hand, had a historical significance. One of the remaining Scouts, Captain Rafael Pabón Cuevas, assaulted Paraguayan Potez pilot 1st Lt. Trifón Bentez Vera on December 4, 1932. The Bolivian dove on Bentez and, despite the Potez’s low altitude, damaged its fuel tank, killing the observer, Captain Ramón Avalos Sánchez, in a second assault from below. Bentez was slain on the third pass, and the Potez was knocked out. Historians used to think this was the first air-to-air victory over the Americas, but it actually happened four months earlier during the Paulista War in Brazil. Nonetheless, this was the first shootdown that resulted in a fatality.

Bolivian forces, under by newly appointed German-born General Hans Kundt, focused their efforts in January 1933 on capturing Nanawa in the south. Four Paraguayan Potezes managed to land under enemy fire, bringing 1.6 tons of much needed supplies, just as the garrison was about to be overrun. Three of them were severely damaged by anti-aircraft fire during the process and were forced to be abandoned in Nanawa, but they were later retrieved and totally reconstructed in Asunción. Because of the great distance between their bases and the front, the Bolivian Hawks and Ospreys flying over the battle zone were unable to intercept them.

Biplanes Battle for Supremacy in South America (Source: Paul Fisher)

On February 25, an Osprey with Captain Arturo Valle Peralta and 1st Lt. José Max Ardiles Monroy was shot down by anti-aircraft fire. During the funeral, two Bolivian Scouts flew over the scene and dropped a floral wreath. The Paraguayans did not fire a single shot at them. 

Bolivians launched five Ospreys, three Hawks, and one Scout to bomb Isla Po airstrip on June 12 after being alerted to the location of the new Paraguayan Fiats. The Paraguayans were notified to the approaching planes by watchtower teams, allowing them to scramble three CR.20s to protect the airport. The Fiats attacked the Ospreys from 8,000 feet, breaking formation, dropping their bombs, and fleeing. Lieutenant Ruffinelli attacked one of the Hawks, who took evasive action, as he turned to confront the Bolivian fighters. Meanwhile, Major Luis Ernst Rivera, a Scout pilot, was following a Fiat piloted by 1st Lt. Walter Gwynn when it abruptly went down and crashed. It’s probable that Gwynn passed out during the dogfight as a result of an injury received in a Fiat accident the week before. Gwynn, a Paraguayan with blonde hair and blue eyes from Welsh parentage, had been urged to stay in the hospital, but he said that “with so many Paraguayan soldiers fighting on foot in the meanwhile, a pilot cannot be in bed.”

There was a considerable gap in air-to-air combat after the June 12 action, but planes continued to carry out ground attacks and artillery correction missions. A huge Paraguayan counterattack spearheaded by Estigarribia through the overextended Bolivian left flank engulfed and killed most of the Bolivian forces facing Nanawa in July, similar to what befell the Germans at Stalingrad late in 1942. Kundt surrendered his command after 10,000 fatalities, and the Bolivians abandoned the entire southern Chaco.

On July 8, 1934, four Paraguayan Potez 25s attacked Ballivián airport on the Pilcomayo River, capturing eight Ospreys on the ground in one of the war’s most severe air battles. The raiders flew over the airfield twice, destroying or damaging a number of Ospreys. The Paraguayans were assaulted by two Ospreys and two Hawks who had arrived from another airport as they were making their third fire pass. Captain Job von Zastrow, manning the dual machine guns in one of the Potezes, claimed an Osprey piloted by Major Eliodoro Nery during the ensuing combat (though the Bolivians said Nery was killed in a training accident nine days later). Meanwhile, 2nd Lt. Fabio Martnez, a Potez observer, was wounded, as was the crew of another Potez, 2nd Lts. Arsenio Vaesken and Cesar Corvalán Doria, who were able to operate their stricken aircraft and maintain a tight formation despite being wounded. As a result, an Osprey piloted by Lt. Alberto Alarcón and Captain Juan Antonio Rivera’s Hawk were damaged, forcing them to flee the combat. Sub Lt. Carlos Lazo de la Vega, the last remaining Hawk pilot, fled as well, now facing the combined fire of eight machine guns. The Paraguayans’ achievements were so widespread that July 8 was designated as National Aviation Day. 

Biplanes Battle for Supremacy in South America During the Battle of Ballivián in 1934, Bolivian pilots Captain Eliodoro Nery, Major Jorge Jordan, and 1st Lt. Juan Antonio Rivera pose with a Junkers K-43 bomber. Nery was assassinated in July, though tales of his death differed. (Photo by Antonio Luis Sapienza, courtesy of Ramiro Molina Alanes)

A Potez was on a reconnaissance mission near Fortin Florida in the northern Chaco on August 12 when its crew noticed a Bolivian Osprey attacking them. At treetop level, the Potez dove and began its normal zig-zagging maneuver. 1st Lt. Rogelio Etcheverry, a paraguayan observer, fired at the Osprey, but the pilot avoided and hit the Potez’s fuselage on his first pass. The Osprey made a second pass, damaging its wings, as the Potez pilot dropped his speed to the point of almost stopping. When the Osprey came on for a third pass, Etcheverry maintained his fire until the adversary was within 250 yards, then opened fire. The Osprey abruptly ceased firing, smoked severely, turned to the left, and slammed into a tree. Etcheverry was surprised to find that he had killed the war’s first air-to-air victor, then-Major Pabón, after the highly damaged Potez landed.

Bolivia swiftly made up for their aircraft losses by bringing in fresh reinforcements in September and October. The “Punta de Alas” (Wingtips) Squadron was armed with nine Curtiss-Wright Cyclone Falcon bombers and three Junkers K-43 bombers. 

The Battle of Ballivián finished on November 14 with a major Paraguayan victory, with the Bolivians losing 15,000 men and being ejected from the Chaco. Two Bolivian Hawks piloted by Lieutenants Alberto Alarcón and Emilio Beltrán shot down a Potez piloted by 2nd Lt. Vaesken that was scouting the El Carmen area on December 11 as a minor consolation. Vaesken dove and landed when the Bolivians damaged the Potez’s engine, surviving but seeing his plane entirely wrecked. To counterbalance this, AA fire crashed a Bolivian Hawk and killed its pilot, Lieutenant Lazo de la Vega, while he was flying a reconnaissance mission in Puesto Central on November 26. 

Bolivian aviation was divided into two combat groups in December 1934: the 1st Aviation Combat Group, directed by Major Jordán of Villa Montes, and the 2nd Aviation Combat Group, led by Major Ernst of Charagua, each with a fighter and bomber squadron, totaling 11-14 planes at any given moment. The active air force of Paraguay had been reduced to four Potezes and two Fiats located at Camacho by that time. 

The Bolivians were able to repel Estigarribia’s assault in Villa Montes, near the oil wells, this time, with all of their aviation assets stationed near the front, but at a cost. A Bolivian Falcon piloted by Lieutenant Aurelio Roca Llano was shot down by anti-aircraft fire over Paraguayan lines on January 12, 1935, and another Falcon piloted by Lt. Alberto Montao was shot down on January 18, 1935. Both shootdowns were carried out with Oerlikon guns acquired from Bolivia by the Paraguayans.

The Paraguayans proceeded further north in February and March, bypassing Villa Montes and crossing the Parapet River to take the battle into Bolivia proper. They occupied Charagua after four Potezes destroyed the 2nd Bolivian Corps headquarters, but a strong counterattack in May drove them back into their own country. During this time, the Bolivians established the 3rd Aviation Combat Group in Puerto Suárez, in the northeast, with two Hawks and one Osprey. Nonetheless, attrition and the transfer of aircraft to other theaters limited the Bolivian 1st and 2nd groups to just two Hawks and one Osprey each when the conflict ended. 

Both forces were in a stalemate by April 1935, with no relief in sight thanks to a Bolivian diversionary attack on the other side of the Chaco that had failed by May 25. Bolivia had lost 67,000 dead, 21,000 captured, and 10,000 fled, mostly to Argen­tina, while Paraguay had seized over 68,000 square miles at a cost of 36,000 dead and 3,800 captured. Disease, mosquitoes, and venomous snakes had claimed as many lives as battle on both sides. Both forces were tired and agreed to an armistice, which took effect on June 12th.

Paraguay was handed three-quarters of the disputed territory in a treaty signed in Buenos Aires on July 21, 1938, but Bolivia was provided an outlet to the Atlantic Ocean via the Paraguay River. The war in—and above—what both sides came to refer to as the “Green Hell” was finally done.  

Javier Garcia de Gabiola is a lawyer who works for a multinational corporation in Spain. He is a dedicated military and aviation historian who has written 50 magazine pieces and his first book, Paulista War: Brazil’s Last Civil War, released in 1932. Further reading: Dan Hagedorn and Antonio L. Sapienza’s Aircraft of the Chaco War 1928-1935; Adrian J. English’s The Green Hell; and Sapienza’s The Chaco Air War 1932-35.

This article was originally published in the July 2023 issue of Aviation History. Make sure you don’t miss an issue by subscribing today!

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