The "military anarchy" of the 3rd century ended in the revolution of the 260s, in which the factual power of the soldiers was institutionalised and the decentralisation of military power in several dozen regional power hubs was politically reigned in (see Military of the Second Roman Republic 263-750). A stronger Roman Republic fights off the invasion of the Huns in the 360s (OTL: 370s) and lashes out against the nomadic threat with the Roman-led Pontic Campaign, which wipes out entire races and brings the steppe from the Carpathians to the Volga under the control of the Second Roman Republic and its allies and proxies.
Rome's strong and dynamic slave-free economy develops quicker than that of its neighbours. It accumulates capital so fast that it continuously seeks investment opportunities in presumably safe neighbouring countries. Roman-owned enterprises thus reap profit from Roman investors throughout countries like Aksum, Sheba, Armenia, Lasika, Iberia, Burgundy, Alemannia etc. The resulting class conflicts thus overlap with nationalist and imperialist notions. One of the resulting wars is the Roman-Aksumite War of the 580s.
A peaceful, thriving Mediterranean empire and economy and the absence of the rise of Islam benefit the development of Aksum and change the nature of the Swahili coast city states. The conflicts resulting from Aksumite imperial expansion lead to the First East African War (756-759).