Egypt was an important province, but the Romans (as I prefer to refer to the Byzantines in this period) were a resourceful bunch and by the end of the century had reconfigured their state to cope with the loss. At the beginning of the seventh century, scholars have estimated that Egypt contributed somewhere between 1.4 to 2.6 million solidi (gold coins) to the imperial treasury, both in taxation and in the grain fleets that sailed to Constantinople. I'm not sure where your figure comes from, as we have no way of knowing how much grain was sent and it must be an estimate (just like the numbers I mentioned). Even so, Egypt was clearly very important and if we work with these estimates and that of other provinces, Egypt by itself would have raised about 35-40% of the income from all the eastern provinces. The still wealthy provinces of the west, North Africa and Sicily, could have perhaps supplied c.400,000 solidi each and, as we will see, would become even more important for the empire as its financial situation deteriorated.^1

But first we need to talk about the civil war of 608-10, in which the governor of North Africa's son, Heraclius, launched his bid for power against Emperor Phocas. Internal strife quickly consumed the Levant and Egypt, with the rebels in the spring of 610 finally seizing control of Egypt and thus became capable of starving the capital into submission. In October that year, Heraclius sailed into Constantinople with his fleet from North Africa and finally deposed Phocas, a quick victory that was probably helped by the fact that he had by now secured Egypt. On this occasion we have no record of the war's financial impact, but we can perhaps infer that with conflict consuming that province, imperial officials did prepare for some sort of contingency plan should the fleets of Alexandria fail to sail, especially as they had two years to do so. For now though Egypt and its wealth remained in imperial hand.

But since 603, the Rome and Persia had been at war, and Roman infighting had provided a golden opportunity for the Persians to seize the east. By 614, Jerusalem was taken and the Persian ruler, Khusro II, was confident enough to reject an offer of utter submission by Heraclius shortly afterwards. The exact details of the campaign are lost, but the Persians then entered Egypt and took Alexandria in 619. This naturally precipitated a crisis in Constantinople - the memory of which would have informed how officials responded to the fall of Egypt in 642, since they had already experienced the same only two decades before. According to a contemporary Constantinopolitan chronicler, in 618 instead of the grain dole being free, three folles were charged for each loaf; by August, even this was cancelled. The scholae, a prestigious regiment in the city, managed to retain their privilege of cheap grain at the new price, but in 626, just before the Avar Siege of Constantinople, an official tried to raise the price further to 8 folles - he failed in the face of public opposition, but it is nevertheless a remarkable indication of the dire financial straits the empire was in.^2

Elsewhere, we know that Heraclius had also melted down church treasures and minted a new silver coin to pay officials rather than paying them with gold, all of which the fall of Egypt must have contributed to (though such things were already happening before 619).^3 Nicephorus' Short History, an eighth-century source that had probably used an earlier source from c.640s, also recorded famine and plague around this point, but without the exact dates.^4 As always when looking at this period, it is hard to quantify exactly the impact of 619. Syria for instance was a very wealthy province in its own right and had been lost much earlier, so it is difficult, if not impossible, to tease out the exact consequences of the fall of Alexandria. Even so, the war of 603-629 nonetheless demonstrates that the Roman empire was entirely capable of surviving without Egypt, in this case even eventually winning the war a decade after losing its eastern provinces.

Our evidence for the 630s is no less clearer than before and we can't be sure to what extent the state managed to reintegrate Egypt into its bureaucracy, but I would be inclined to say that they did the best they could, making its eventual loss in 642 an all the more disastrous one. We know from the papyri evidence that the Persians in Egypt essentially used Roman institutions for their own profit, so it is logical that the Romans could then do the same, except now directing Egyptian taxes to Constantinople.^5 It is true that we have no evidence for the grain dole (or just subsidised grain) being restored, but that may be simply due to the lack of sources for this period and even if this is true, it tells us nothing about how the treasury exploited Egypt's wealth by taxation. From other sources we learn that the empire was still dealing with financial problems and that Heraclius would order a census c.640, an important step towards rebuilding the taxation system; between these scraps of evidence, I think it is clear that the Romans were absolutely desperate for money and hence would have exploited Egypt to the best of their ability. An inordinate amount of effort was also spent on governing the province itself - Cyrus, an imperial favourite from the Caucasus, was parachuted into the patriarchate of Alexandria and proceeded to achieve great success in reconciling with the schismatic miaphysite church of Egypt (who were the majority, as opposed to the minority of Chalcedonian Christians). A truce, bought with tribute to the Arabs, was also probably in place c.636-9, even as Roman armies tried to stop the Arab advance in the Levant, which to me is yet another indication of the necessity for the Roman state to retain Egypt and keep out military threats.^6

By all accounts, the treaty of 641 with the Arabs agreeing to handover the province in 642 was a disaster and recognised as such by contemporaries. Yet it was also the product of infighting in Constantinople, as there were two factions vying for control in 641, a year of four emperors. Heraclius had left his two eldest sons as co-emperors after his death that year: Heraclius Constantine and Heraclonas. The former can be said to be of the 'war' party, which favoured continuing the fight no matter the odds, whilst the latter preferred accommodation, at least when the military situation was hopeless. The treaty of 641 was negotiated when the 'peace' party was in power, but when the 'war' party took power shortly afterwards and criticised everything the 'peace' party had implemented, they did not renege on this treaty. The Roman state had already been weakened greatly and there was no possibility of them taking back Egypt in the near future.^7

There were however contingency plans in place, as they had a whole year to prepare for the consequences of losing Egypt. Already in the 620s, officials known as the kommerkiarioi were in place in Africa to secure grain for the government and evidence for them appear in Sicily around the middle of the century as well.^8 As the empire's military situation in the east collapsed, bureaucrats had already begun to exploit more fully the resources of the west. Scholars debate the exact role of the kommerkiarioi, but regardless of their positions, the surge in kommerkiarioi seals found in this period in the west is to me prove enough of their importance in financing the state, even if the details are still disputed.^9 It is also at this point that we can also point to the growth of imperial influence in Sicily, steadily eroding papal patronage, which is a fairly significant indication of the province's importance to Constantinople.^10 Together with North Africa, Sicily fed the imperial capital and in the 650s and 660s we have evidence of an increase in western exports found in Constantinople, along with other signs of an intensification of governance on islands such as Cyprus, all of which point to the Romans adapting to their new situation.^11 It should be no surprise then that from 663 onwards the emperor of the Romans, Constans II (641-668) ruled his empire from Syracuse - where better to rule than from the chief source of his income?^12

This is of course not the entire story and we do need to point to other factors, for example environmental change, which boosted agricultural yields in Anatolia in the seventh century and thus allowed more food to be produced precisely where the empire needed to feed its garrisons.^13 But I hope my explanation of the events is useful as well, if only to shed some light on the still under-studied nature of Roman government in this period. In more general terms, this century was indeed a time of war and cultural change, but a picture of 'decline' is not an accurate one, since the Romans adapted to the new much poorer circumstances, a rare feat for a polity facing such misfortunes. The loss of Egypt, despite its prized status, did not signify the collapse of the empire, since Constantinople endured the crises of both 619 and 642 and these losses had also prompted new innovations within the state to cope with the financial burden. In my view, the Roman empire thus amply deserves the description given in a new monograph on this very topic: the empire that would not die.