How about trade posts and proselytizing missions, with hope of recruiting locals for both, in Africa instead of colonizing the whole place?
East Africa is Ethiopian/Omani turf and they would not appreciate the competition. Meanwhile Atlantic Africa has nothing of interest to Rhomania; anything it can provide can also be provided by East Africa, which is closer.
The Algiers Expedition
In the west, the Regency of Athena was extremely quiet in foreign affairs, with the one exception of the Algiers expedition. This was not a popular move in the halls of the White Palace. The expense was something that the exchequer very much wished to avoid while the benefits of any success would accrue mostly to the Latins and Sicilians. Since Roman shipping rarely went west of Sardinia anymore and Roman shores were far away with Sicily in the way, corsairs were not a notable problem.
The Roman contribution was solely because of commitments made in the negotiations over Italy, but the feeling was that Latin problems should be dealt with by Latins using their own men and money. As for the Sicilians, there was animus against them because of their perceived betrayal over the matter of Italy, which only irritated the Sicilians who were not impressed by Roman sour grapes over what the Sicilians considered the reasonable defense of their legal rights and interests.
The expedition is set for 1642, with the various allied fleets to rendezvous in Minorca, the island holding of the Hospitaler Order. However due to delays of raw material shipments needed for maintenance, the Roman contingent is delayed in departing Rhomania and further slowed by contrary winds in making its journey across the Mediterranean. As a result, when the Romans finally arrive in Minorca, the ships of the Order, Spain (which includes some Aragonese vessels), Arles, the Kingdom of the Isles, and Sicily all have been there for at least three weeks.
Thus the various allies are not in a particularly good mood when the Romans arrive. The enforced three weeks of idleness has been a voracious pit devouring their limited supply of moneys and victuals. Furthermore the crowded conditions are inevitably unhygienic, with disease outbreaks beginning to affect the crews.
The Romans try to explain the delay away by the material factors, but they fail to mollify the allies for various reasons. One is that the Roman contingent is somewhat underwhelming, not justifying the delay. The Spanish provided 22 ships, the Arletians 14, the Sicilians 16, the Order 6, and the Islanders 4 (the Order and Islander ships are combined into one squadron for tactical and administrative purposes). The Romans bring 15 ships to the armada.
Another reason is the behavior of the Roman commander, Navarchos Andronikos Platanas. Historians are divided on the question of whether Platanas was ordered by the White Palace to try and sabotage the expedition, or if the tensions were the result of his personality.
(Leo Kalomeros has been transferred to the Mediterranean by this point, but is not part of the expedition. Some historians argue that this was because it was felt that given his recent battle experiences with the Spanish, he would be a poor choice as part of a fleet that was operating with Spaniards. However there is no direct evidence of this and if that was the rationale for excluding Kalomeros, it makes the inclusion of Platanas even more puzzling. It should also be noted that at this point Kalomeros was still a junior officer with no ability to demand assignments, and so his inclusion or absence was not a matter of priority.)
The various allies have not been completely idle while waiting for the Romans. While the Commander-in-Chief of the combined fleet is to be the Hospitalier Grandmaster, Pierre de Monte, as agreed upon beforehand, he is not to become autocratic commander of all units. National pride won’t allow that. So the allies draw up Articles of War to govern the conduct of the combined fleet.
Tactically the fleet is divided into national squadrons to be commanded by their own officers, with the Grandmaster having complete command authority during battle. The various officers recognize the need for a clear and simple chain of command when shot is flying. However all important strategic decisions are to be made by a Council of War. The Council is to be comprised of the three senior officers from each national contingent, Hospitalers & Islanders, Spanish, Arletians, Sicilians, and Romans. Voting is to be done publicly and in rotation, with the senior most officer of each contingent voting first, to be followed by the second-most of all contingents, and then the third, although voting will cease once a majority is reached. The Hospitaler & Islander contingent, because it contains the Commander-in-Chief, gets first vote in the rotation. The order of the others is determined by lot, with it going Sicilian, Arletian, and Spanish. The Romans, because they are not present when all this is decided, are given the last slot.
Platanas is outraged that Articles of War have been drawn up that will govern the Romans without Roman input, and he wants new ones drawn up. However the other allies just want to get the expedition going already. For the sake of expediency, Platanas says he will agree to the Articles but demands that the Romans take the second slot after the Hospitalers & Islanders. This is rejected since in neither hulls nor weight-of-shot can the Romans justify preeminence; if that determined precedence as opposed to chance, the Spanish would take it. Eventually, after much argument and time during which at least a hundred allied sailors die of disease, Platanas agrees to the Articles provided the precedence-determining lots be cast again. This is accepted with the lots cast. The Romans still get the last slot, much to the amusement of the allied officers and the rage and fury of Platanas.
Finally the fleet sets sail, after a meeting that determines its target. For all the disputation over how the war council was to operate, the first meeting is quick for the target is obvious: Algiers. Corsairs operate from many ports along the North African coast, and are not restricted even to the Mediterranean, with the rovers of Sale on Morocco’s Atlantic coast raiding as far away as the Grand Banks.
But Algiers is by far the greatest of the pirate ports. In 1640 it has around 60,000 inhabitants, with ten to fifteen thousand of them slaves, mostly European although some are Africans purchased from the Sahara trade. That same year 61 corsair vessels put out to sea, hitting targets from Brittany to Crete. In the last case the corsairs seized 31 people, fishermen and sailors working small coaster trading vessels; Rhomania suffers much less than the western Mediterranean but is not immune.
Many of the corsairs are of North African stock, but many are not. The exceptions are European renegades, many (but not all of whom) have converted to Islam. Some were drawn to the lifestyle and opportunities for riches and advancement offered by the corsair lifestyle. Others are captives who when taken prisoner were offered the choice of being a slave or a corsair and took the latter course.
Algiers is nominally subject to the Marinid Sultan, but were he to abolish piracy, he would be ignored. It is vital to the prosperity of Algiers and the elite of the city are too invested in the practice to give it up. While there is a governor of the city, there is also a guild of captains, comprised of the senior corsairs, that is a major locus of power in Algiers. They are not going to give up their way of life, and the profits from it, easily.
The commander of the coastal artillery, Mohammed Pasha, an Arletian renegade and convert to Islam (he was captured on his family’s fishing boat as a boy), makes that quite clear when the Grandmaster makes his demands. He straps an elderly Spanish priest to the muzzle of one of his guns and threatens to blow him, and more prisoners, from his cannon if the allies attack. The allies are not dissuaded, with the first shot of the battle killing the priest. At least twenty more Algerian prisoners are murdered in similar fashion. [1]
The battle of Algiers (1642) is a fierce gunnery duel between the allied fleet and the coastal defenses of Algiers. The allies are restricted to naval options as they have little in the way of army units save for sharpshooters posted on vessels for additional firepower. The last serious incursion into North Africa, a Roman venture, was demolished by a Marinid army 50,000 strong. The allies don’t have the sealift capacity to move an army big enough to challenge that, so they don’t even try. It is just as well. Considering the supply and sanitation situation on Minorca, adding soldiers to the mix would just have increased the death toll.
Three of the Spanish vessels are bomb ketches which have proven their worth in the Andalusi war, their high-angle long-range heavy mortars wreaking havoc on the city while the conventional ships engage the coastal batteries. Firing is hot and thick, both sides taking heavy losses. The Great Mosque of Algiers is damaged by the bomb ketches and many harbor guns are put out of action. But those harbor guns did not go down quietly, the batteries along the Grand Mole proving particularly dangerous. The Spanish flagship alone is hit over two hundred times. Both sides distinguish themselves, with the conspicuous exception of the Romans who stand off and engage in an ineffectual long-range cannonade. Three Roman vessels break from this pattern, moving in closer to fire more effectually; they are reprimanded and recalled by Platanas.
At dusk the duel ends, both sides licking their wounds. The mood in the council of war is ugly. Losses are heavy, much powder and shot has been expended, supplies are running low, disease is still raging in the crews, and everyone is utterly fed up with Platanas. To his face, the Spanish admiral (whose nephew, serving as an aide, lost a foot that day to a shot from one of the mole batteries) tells him that if Platanas was his subordinate, he’d have him hanged from a yardarm for cowardice in the face of the enemy.
The Algerians rub salt in the wound the next morning by offering, as a gesture of goodwill, to release thirty five captives gratis. They are all Romans, which confirms in the eyes of practically all of the allied officers that Platanas is in league with the Algerians.
Combined with all these issues, it is late in the season and many an expedition against Algiers has met bloody ruin by the wrath of Mother Nature in these waters. Thus the expedition breaks up with bitter recriminations. Despite the expenditure and effort and the thousands of shot fired into Algiers, it would seem that this attack on Algiers, like the many before it, is a bloody failure.
But it is not a total failure. Unlike those earlier attacks, this one did inflict serious harm on Algiers and cause many casualties amongst the mariner population that crews the corsair ships. In 1643, thirty five put out to sea. And in another way this is different from earlier assaults, as the 1642 attack is not a one-shot but is followed up by renewed effort.
In 1644 a fresh allied force puts out to sea, with Spanish, Aragonese, Hospitalier, Islander, Arletian, and Sicilian contributions. The Romans are not invited. (Platanas returns to Constantinople and faces neither commendation nor condemnation, giving no hint as to whether he was acting on orders or if his personality was just spectacularly unsuited for the task.)
This fleet sets sail much earlier, in much better health and provisions, and with more shot and powder. Again the guns sound, both sides taking heavy losses, but the allies keep up the attack and after three days of shelling they are clearly getting the better of the exchange. The city of Algiers is finally forced to come to terms.
Surrender is not unconditional and the Algerians are stubborn bargainers. But they are forced to relinquish a thousand captives and allow three thousand more to be ransomed. Allied efforts to get more run into the stumbling block that many of the captives are private property, not slaves of the state, and their masters are reluctant to part with them. So while many slaves are freed, many more remain in bondage.
The Algerians are also forced to sign pledges not to attack the shipping of the allied powers. Again this is difficult to enforce because corsairs tend to ignore orders they don’t like, and piracy and slavery are essential for maintaining Algiers’s economy at its current level of development. Still it is a success, even if not a complete one. Corsairs still put out from Algiers, but in 1645 their ships only number twenty three, and they never again attain the numbers or reach that they held before 1644.
[1] This is from the OTL French bombardment of Algiers in 1683.