In the year 1824, Sultan Mahmud, realising the impossibility of putting down the Greek insurrection by his own unaided forces, bent his pride sufficiently to ask help of his vassal Mehemet Ali. Mehemet was now in possession of a well-drilled army and a well-equipped fleet, which were placed at the service of the sultan, who promised him in return the sovereignty of Crete, the pashalic of Syria, and possibly the reversion of Morea for his son Ibrahim. The Greeks, deceived by their easy successes over the undisciplined Turkish hosts, failed to realise the greatness of the danger which threatened them. The Egyptian fleet managed, without serious opposition, to enter the Archipelago, and, in December, 1824, Ibrahim, to whom Mehemet Ali had entrusted the supreme command of the expedition, established his base in Crete, within striking distance of the Greek mainland. The following February he landed with four thousand regular infantry and five hundred cavalry at Modon, in the south of Morea. The Greeks were utterly unable to hold their own against the well-disciplined fellaheen of Ibrahim Bey, and, before the end of the year, the whole of the Peloponnesus, with the exception of a few strongholds, was at the mercy of the invader, and the report was spread that Ibrahim intended to deport the Greek population and re-people the country with Moslem negroes and Arabs. The only barrier opposed to the entire extinction of the Greek population was their single stronghold of Missolonghi, which was now besieged by Rashid Pasha and the Turks. If Ibrahim had joined his forces with the besieging army of the Turks, Missolonghi could hardly have resisted their combined attack, and the Greek race would have been in danger of suffering annihilation. Meanwhile the Great Powers of Europe were seriously concerned with this threatened destruction of the Greeks. England proposed a joint intervention in defence of Greece on the part of the Powers, but Russia desired to act alone. A huge army was gradually concentrated upon the Turkish frontier. The Greek leaders now offered to place Greece under British protection, and the Duke of Wellington was sent to St. Petersburg to arrange the terms of the proposed joint intervention. A protocol was signed at St. Petersburg April 4, 1826, whereby England and Russia pledged themselves to cooperate in preventing any further Turco-Egyptian agression. A more definite agreement was reached in September, aiming at the cutting off of Ibrahim in Morea by a united European fleet, thus forcing the Turks and Egyptians to terms. On July 6,1827, a treaty was signed at London, between England, France, and Russia, which empowered the French and English admirals at Smyrna to part the combatants--by peaceful means if possible, and if not, by force.