Discovery of a direct sea route to India: open-sea travel and the Bab el-Mandeb barrier

The issue of discovery of a sea route to India is one of the most important questions about Indo-Roman trade relations and it has yet to be resolved. Historians tend to focus on who and when made the first open-sea journey, and whether it was a sudden change or a process. Conditions essential for discovery of a new route are not considered (not clear – are not considered here, in this paper?), nor are the circumstances that would have made this journey possible. Another issue (of what?) is the case of the Arabia Eudaimon port. The 1st-century AD Periplus Maris Erythraei states that the port had been ransacked and there was no direct connection between India and Egypt, but that all ships were forced to stop there. Thus the resumption of active trade with India necessitated the lifting of the tentative blockade of Arabia Eudaimon and discovering the trans-oceanic route. The nautical guide, however, does not describe the new repute in the context of the troubles in Bab el-Mandeb, but can we be really sure that these two events were not related? What were the circumstances and conditions that had to be met for it to be possible to discover a new route?