Final answer:
The Messenians and the four nations both exhibited military strength and engineering expertise. This is demonstrated through their elite military forces and advanced engineering practices, common traits in the dynamic Mediterranean region's cultures.
Step-by-step explanation:
The cultural characteristic that both the Messenians and the four nations shared was military strength and engineering expertise. Throughout the Mediterranean, the various cultures such as the Greeks, the Etruscans, and the Phoenicians displayed dynamic military capabilities, often employing elite warriors and engaging in continuous trade and warfare, which over time necessitated advanced engineering techniques for both military and civilian purposes. The Greeks, for instance, excelled in creating strategic military forces and in-engineering skills necessary for infrastructure and trade, as evidenced by the prowess of Hellenistic soldiers and the infrastructural remains of cities like Ai Khanum.