From the beginning, Bilbao Rioja ordered the aircraft to conduct aggressive patrols over the Chaco, and the Bolivians lost at least one Vickers Vespa due to anti-aircraft fire at the end of July. During the Battle of Boquerón, both sides carried out numerous attacks in support of ground troops. Between 9 and 29 September, Paraguayan Potez 25s, escorted by Wibault 73 fighters, carried out 12 bombing raids against Bolivian troops in Boqueron. The Paraguayans also used their radio-equipped Potez 25s to direct artillery fire from their Schneider 75 mm batteries. Though both sides flew reconnaissance and close air support missions during the Boqueron Campaign, there is disagreement about the first air-to-air confrontation:  The first encounter between fighters over the Chaco took place on 12 June 1933, as five Ospreys were being escorted by three Hawks and one Vickers Scout in the course of an airstrike against Isla Poí. The Fiats disrupted the Bolivian package in the middle of a furious dogfight. Lieutenant Walter Gwynn's CR.20, however, crashed in the aftermath, killing the pilot. A Paraguayan technical team ruled out hostile fire as the cause of this loss. The Fiats engaged the Ospreys again on 23 September 1934 over Picuiba, when two Bolivian warplanes were spotted while involved in a bombing mission. One of the Ospreys jettisoned its bombs and escaped unscathed, but the other pilot only became aware of the enemy fighters when he noticed the loss of his wingman. The Fiats duly targeted the lonely plane with their machine guns. The Paraguayans claimed the second Osprey as "probable", but the Bolivian aircraft managed to fly back to its base, although seriously damaged. The Paraguayan army would lose another Potez 25 to Bolivian planes on 12 December 1934 over Capirenda, when a Hawk escorting a Junkers K 43 shot down Potez TOE Nº 13 after a brief exchange of fire. Both pilot and gunner survived the crash. The conflict would see the last ever dogfight between biplanes, over the Bolivian stronghold of Ballivián. The Potez 25 would be the only type of aircraft from either side to be used during the entire conflict. The aerial forces played a variety of important roles at all stages of the war, including close air support, reconnaissance, air supply and evacuation of the wounded.