Fortifications. Angolan armies at times made extensive use of fortifications. In a 1585 campaign against the Portuguese, the Ndongo for example constructed palisaded camps, each a day's journey apart. Use of strong defensive positions on hilltops or in forests was also common, as was the use of fortifications in offensive maneuvers. The Imbangala for example usually built a strong fort in enemy territory to bait opponents into exhausting their strength against it. Some of these positions could be quite formidable, with trenches, parapets, hidden roads, sharpened "punji" stake traps, mutually supporting bulwarks, and covered trenches to protect against artillery. Two-way borrowing and adaptation. Firearms were gradually adopted by the Angolan militaries and used alongside customary fighting implements. Soldiers from the state of Kasanje in the 18th century for example, marched with bows and lances as well as muskets. Their gunmen were considered to be the equal of the Portuguese in competence. While Portuguese mercenaries and armies armed with muskets made a substantial showing in military terms, it was only until the end of the 18th century than indigenous forces incorporated them on a large scale. Other gunpowder weapons like artillery served the Portuguese well in breaking up enemy attacks or against fortifications. African systems like that of Kongo also gradually adopted artillery though on a much more limited scale. Ironically the Portuguese were sometimes more effective because of "non-firearm" weapons, such as body armor, swords and pikes. The exchange of techniques and approaches was not always one way. While the Kongo kingdoms gradually adopted European technology, the Portuguese themselves borrowed and adapted African war practices to make themselves more effective against their opponents. In one engagement, the Battle of Kitombo, in 1670, the Portuguese armed themselves with native shields, hoping to demonstrate their prowess with these and their swords. The Portuguese adopted some indigenous practices such as the use of quilted cotton armor, proof against arrows and light spears. They also drew heavily on native allies, keeping a small nucleus of European troops, and a large body of indigenous warriors- with each force fighting in its own style. This is similar to the Kongo use of allied forces. The Europeans also adopted the looser formation of the native armies, discarding rigid squares of musketeers for more maneuverable and flexible configurations. Typical of Phoenician settlements, the navy of Carthage was the city's military backbone, and the prime force that dominated the Western Mediterranean at the height of Carthage's power.