On 16 August, Portuguese cavalry and African auxiliaries spotted a build-up of Ovambo troops in Mongua, near a few small water-holes. Pereira de'Eça ordered his men towards that direction, and the next day they set up defensive positions just like Mandume's men. On 18 August, a close friend of Mandume, Calola, with a force of Ovambo men attacked the eastern and northern flank with all force starting the Battle of Mongua. Pereira de'Eça's men responded with a rain shower of bullets for 3 hours. In total, one officer and 16 privates were killed on the Portuguese side. Afterward, the Ovambo surrounded the Portuguese forces and forced them to dig in. That same day the two fought over a water-hole because both were low on resources. The next day Mandume come to the area with reinforcements. On 20 August, Mandume assembled several thousand men and attacked the Portuguese camp shouting "The land does not belong to the white[s]!”. After 10 hours of fighting, the Ovambo were forced to retreat due to a lack of supplies including the water which they had lost. In total, the Portuguese took 35 casualties and had 57 wounded. The Ovambo lost 25 and had 100 wounded. After the battle, the Portuguese also started claiming that German forces were helping the Ovambo because it was unimaginable to them that Africans were able to wage war like Europeans.
