Defining the shape of The Isle of Thanet when it was a island and when the Romans is basically guesswork based on what we know now.
I have drawn a red circle around where we now know the Romans first landed over 2,000 years ago, and think it would make sense for them to have taken Isle of Thanet as a defensive position to fight off the Britons (mostly painted blue) who were probably very angry.
It also makes some sense that the Romans built forts at Reculver and Richborough to stop anyone using the same strategy to retake the country from them.
This map is even older, but not old enough. Tenet is Latin for Thanet
The Gallic Wars are described by Julius Caesar in his book Commentarii de Bello Gallico, here is the bit of his book where he describes wot went on ere.
While Caesar remains in these parts for the purpose of procuring ships, embassadors come to him from a great portion of the Morini, to plead their excuse respecting their conduct on the late occasion; alleging that it was as men uncivilized, and as those who were unacquainted with our custom, that they had made war upon the Roman people, and promising to perform what he should command. Caesar, thinking that this had happened fortunately enough for him, because he neither wished to leave an enemy behind him, nor had an opportunity for carrying on a war, by reason of the time of year, nor considered that employment in such trifling matters was to be preferred to his enterprise on Britain, imposes a large number of hostages; and when these were brought, he received them to his protection. Having collected together, and provided about eighty transport ships, as many as he thought necessary for conveying over two legions, he assigned such [ships] of war as he had besides to the quaestor, his lieutenants, and officers of cavalry. There were in addition to these eighteen ships of burden which were prevented, eight miles from that place, by winds, from being able to reach the same port. These he distributed among the horse; the rest of the army, he delivered to Titurius Sabinus and L. Aurunculeius Cotta, his lieutenants, to lead into the territories of the Menapii and those cantons of the Morini from which embassadors had not come to him. He ordered Sulpicius Rufus, his lieutenant, to hold possession of the harbour, with such a garrison as he thought sufficient.
These matters being arranged, finding the weather favourable for his voyage, he set sail about the third watch, and ordered the horse to march forward to the further port, and there embark and follow him. As this was performed rather tardily by them, he himself reached Britain with the first squadron of ships, about the fourth hour of the day, and there saw the forces of the enemy drawn up in arms on all the hills. The nature of the place was this: the sea was confined by mountains so close to it that a dart could be thrown from their summit upon the shore. Considering this by no means a fit place for disembarking, he remained at anchor till the ninth hour, for the other ships to arrive there. Having in the mean time assembled the lieutenants and military tribunes, he told them both what he had learned from Volusenus, and what he wished to be done; and enjoined them (as the principle of military matters, and especially as maritime affairs, which have a precipitate and uncertain action, required) that all things should be performed by them at a nod and at the instant. Having dismissed them, meeting both with wind and tide favorable at the same time, the signal being given and the anchor weighed, he advanced about seven miles from that place, and stationed his fleet over against an open and level shore.
But the barbarians, upon perceiving the design of the Romans, sent forward their cavalry and charioteers, a class of warriors of whom it is their practice to make great use in their battles, and following with the rest of their forces, endeavored to prevent our men landing. In this was the greatest difficulty, for the following reasons, namely, because our ships, on account of their great size, could be stationed only in deep water; and our soldiers, in places unknown to them, with their hands embarrassed, oppressed with a large and heavy weight of armor, had at the same time to leap from the ships, stand amid the waves, and encounter the enemy; whereas they, either on dry ground, or advancing a little way into the water, free in all their limbs in places thoroughly known to them, could confidently throw their weapons and spur on their horses, which were accustomed to this kind of service. Dismayed by these circumstances and altogether untrained in this mode of battle, our men did not all exert the same vigor and eagerness which they had been wont to exert in engagements on dry ground.
When Caesar observed this, he ordered the ships of war, the appearance of which was somewhat strange to the barbarians and the motion more ready for service, to be withdrawn a little from the transport vessels, and to be propelled by their oars, and be stationed toward the open flank of the enemy, and the enemy to be beaten off and driven away, with slings, arrows, and engines: which plan was of great service to our men; for the barbarians being startled by the form of our ships and the motions of our oars and the nature of our engines, which was strange to them, stopped, and shortly after retreated a little. And while our men were hesitating [whether they should advance to the shore], chiefly on account of the depth of the sea, he who carried the eagle of the tenth legion, after supplicating the gods that the matter might turn out favorably to the legion, exclaimed, "Leap, fellow soldiers, unless you wish to betray your eagle to the enemy. I, for my part, will perform my duty to the commonwealth and my general." When he had said this with a loud voice, he leaped from the ship and proceeded to bear the eagle toward the enemy. Then our men, exhorting one another that so great a disgrace should not be incurred, all leaped from the ship. When those in the nearest vessels saw them, they speedily followed and approached the enemy.
The battle was maintained vigorously on both sides. Our men, however, as they could neither keep their ranks, nor get firm footing, nor follow their standards, and as one from one ship and another from another assembled around whatever standards they met, were thrown into great confusion. But the enemy, who were acquainted with all the shallows, when from the shore they saw any coming from a ship one by one, spurred on their horses, and attacked them while embarrassed; many surrounded a few, others threw their weapons upon our collected forces on their exposed flank. When Caesar observed this, he ordered the boats of the ships of war and the spy sloops to be filled with soldiers, and sent them up to the succor of those whom he had observed in distress. Our men, as soon as they made good their footing on dry ground, and all their comrades had joined them, made an attack upon the enemy, and put them to flight, but could not pursue them very far, because the horse had not been able to maintain their course at sea and reach the island. This alone was wanting to
The enemy being thus vanquished in battle, as soon as they recovered after their flight, instantly sent ambassadors to Caesar to negotiate about peace. They promised to give hostages and perform what he should command. Together with these ambassadors came Commius the Altrebatian, who, as I have above said, had been sent by Caesar into Britain. Him they had seized upon when leaving his ship, although in the character of ambassador he bore the general's commission to them, and thrown into chains: then after the battle was fought, they sent him back, and in suing for peace cast the blame of that act upon the common people, and entreated that it might be pardoned on account of their indiscretion. Caesar, complaining, that after they had sued for peace, and had voluntarily sent ambassadors into the continent for that purpose, they had made war without a reason, said that he would pardon their indiscretion, and imposed hostages, a part of whom they gave immediately; the rest they said they would give in a few days, since they were sent for from remote places. In the mean time they ordered their people to return to the country parts, and the chiefs assembled from all quarter, and proceeded to surrender themselves and their states to Caesar.
A peace being established by these proceedings four days after we had come into Britain, the eighteen ships, to which reference has been made above, and which conveyed the cavalry, set sail from the upper port with a gentle gale, when, however, they were approaching Britain and were seen from the camp, so great a storm suddenly arose that none of them could maintain their course at sea; and some were taken back to the same port from which they had started; - others, to their great danger, were driven to the lower part of the island, nearer to the west; which, however, after having cast anchor, as they were getting filled with water, put out to sea through necessity in a stormy night, and made for the continent.
It happened that night to be full moon, which usually occasions very high tides in that ocean; and that circumstance was unknown to our men. Thus, at the same time, the tide began to fill the ships of war which Caesar had provided to convey over his army, and which he had drawn up on the strand; and the storm began to dash the ships of burden which were riding at anchor against each other; nor was any means afforded our men of either managing them or of rendering any service. A great many ships having been wrecked, inasmuch as the rest, having lost their cables, anchors, and other tackling, were unfit for sailing, a great confusion, as would necessarily happen, arose throughout the army; for there were no other ships in which they could be conveyed back, and all things which are of service in repairing vessels were wanting, and, corn for the winter had not been provided in those places, because it was understood by all that they would certainly winter in Gaul.
On discovering these things the chiefs of Britain, who had come up after the battle was fought to perform those conditions which Caesar had imposed, held a conference, when they perceived that cavalry, and ships, and corn were wanting to the Romans, and discovered the small number of our soldiers from the small extent of the camp (which, too, was on this account more limited than ordinary, because Caesar had conveyed over his legions without baggage), and thought that the best plan was to renew the war, and cut off our men from corn and provisions and protract the affair till winter; because they felt confident, that, if they were vanquished or cut off from a return, no one would afterward pass over into Britain for the purpose of making war. Therefore, again entering into a conspiracy, they began to depart from the camp by degrees and secretly bring up their people from the country parts.
But Caesar, although he had not as yet discovered their measures, yet, both from what had occurred to his ships, and from the circumstance that they had neglected to give the promised hostages, suspected that the thing would come to pass which really did happen. He therefore provided remedies against all contingencies; for he daily conveyed corn from the country parts into the camp, used the timber and brass of such ships as were most seriously damaged for repairing the rest, and ordered whatever things besides were necessary for this object to be brought to him from the continent. And thus, since that business was executed by the soldiers with the greatest energy, he effected that, after
While these things are being transacted, one legion had been sent to forage, according to custom, and no suspicion of war had arisen as yet, and some of the people remained in the country parts, others went backward and forward to the camp, they who were on duty at the gates of the camp reported to Caesar that a greater dust than was usual was seen in that direction in which the legion had marched. Caesar, suspecting that which was [really the case], - that some new enterprise was undertaken by the barbarians, ordered the two cohorts which were on duty, to march into that quarter with him, and two other cohorts to relieve them on duty; the rest to be armed and follow him immediately. When he had advanced some little way from the camp, he saw that his men were overpowered by the enemy and scarcely able to stand their ground, and that, the legion being crowded together, weapons were being cast on them from all sides. For as all the corn was reaped in every part with the exception of one, the enemy, suspecting that our men would repair to that, had concealed themselves in the woods during the night. Then attacking them suddenly, scattered as they were, and when they had laid aside their arms, and were engaged in reaping, they killed a small number, threw the rest into confusion, and surrounded them with their cavalry and chariots.
Their mode of fighting with their chariots is this: firstly, they drive about in all directions and throw their weapons and generally break the ranks of the enemy with the very dread of their horses and the noise of their wheels; and when they have worked themselves in between the troops of horse, leap from their chariots and engage on foot. The charioteers in the mean time withdraw some little distance from the battle, and so place themselves with the chariots that, if their masters are overpowered by the number of the enemy, they may have a ready retreat to their own troops. Thus they display in battle the speed of horse, [together with] the firmness of infantry; and by daily practice and exercise attain to such expertness that they are accustomed, even on a declining and steep place, to check their horses at full speed, and manage and turn them in an instant and run along the pole, and stand on the yoke, and thence betake themselves with the greatest celerity to their chariots again.
Under these circumstances, our men being dismayed by the novelty of this mode of battle, Caesar most seasonably brought assistance; for upon his arrival the enemy paused, and our men recovered from their fear; upon which thinking the time unfavorable for provoking the enemy and coming to an action, he kept himself in his own quarter, and, a short time having intervened, drew back the legions into the camp. While these things are going on, and all our men engaged, the rest of the Britons, who were in the fields, departed. Storms then set in for several successive days, which both confined our men to the camp and hindered the enemy from attacking us. In the mean time the barbarians dispatched messengers to all parts, and reported to their people the small number of our soldiers, and how good an opportunity was given for obtaining spoil and for liberating themselves forever, if they should only drive the Romans from their camp. Having by these means speedily got together a large force of infantry and of cavalry they came up to the camp.
Although Caesar anticipated that the same thing which had happened on former occasions would then occur - that, if the enemy were routed, they would escape from danger by their speed; still, having got about thirty horse, which Commius the Atrebatian, of whom mention has been made, had brought over with him [from Gaul], he drew up the legions in order of battle before the camp. When the action commenced, the enemy were unable to sustain the attack of our men long, and turned their backs; our men pursued them as far as their speed and strength permitted, and slew a great number of them; then, having destroyed and burned every thing far and wide, they retreated to their camp.
The same day, embassadors sent by the enemy came to Caesar to negotiate a peace. Caesar doubled the number of hostages which he had before demanded; and ordered that they should be brought over to the continent, because, since the time of the equinox was near, he did not consider that, with his ships out of repair, the voyage ought to be deferred till winter. Having met with favorable weather, he set sail a little after midnight, and all his fleet arrived safe at the continent, except two of the ships of burden which could not make the same port which the other ships did, and were carried a little lower down.
When our soldiers, about 300 in number, had been drawn out of these two ships, and were marching to the camp, the Morini, whom Caesar, when setting forth for Britain, had left in a state of peace, excited by the hope of spoil, at first surrounded them with a small number of men, and ordered them to lay down their arms, if they did not wish to be slain; afterward however, when they, forming a circle, stood on their defense, a shout was raised and about 6000 of the enemy soon assembled; which being reported, Caesar sent all the cavalry in the camp as a relief to his men. In the mean time our soldiers sustained the attack of the enemy, and fought most valiantly for more than four hours, and, receiving but few wounds themselves, slew several of them. But after our cavalry came in sight, the enemy, throwing away their arms, turned their backs, and a great number of them were killed.
The day following Caesar sent Labienus, his lieutenant, with those legions which he had brought back from Britain, against the Morini, who had revolted; who, as they had no place to which they might retreat, on account of the drying up of their marshes (which they had availed themselves of as a place of refuge the preceding year), almost all fell into the power of Labienus. In the mean time Caesar's lieutenants, Titurius and Cotta, who had led the legions into the territories of the Menapii, having laid waste all their lands, cut down their corn and burned their houses, returned to Caesar because the Menapii had all concealed themselves in their thickest woods. Caesar fixed the winter quarters of all the legions among the Belgae. Thither only two British states sent hostages; the rest omitted to do so. For these successes, a thanksgiving of twenty days was decreed by the senate upon receiving Caesar's letter.