This is the 6584th most frequent Spanish word.
cartaginés
"Cartaginés" refers to something or someone from or related to Cartagena (in Spain or Colombia) or Carthage (an ancient city in present-day Tunisia).
Here, 'cartaginesa' is used as an adjective describing the naval strategy related to Carthage.
Mi amigo está estudiando la estrategia naval cartaginesa en la universidad.
My friend is studying Carthaginian naval strategy at the university.
In this example, 'cartaginesa' is again an adjective, this time qualifying 'influencia arquitectónica' with respect to Carthage.
La influencia arquitectónica cartaginesa se puede observar en algunos edificios de la región.
The Carthaginian architectural influence can be observed in some buildings of the region.
In this sentence, 'cartagineses' is used as a plural noun referring to the people from Carthage.