Doubtless the Spaniards would at once have moved on against Sicily; but France and England now intervened more actively to prevent the general war that seemed threatening. England sent a fleet to the Mediterranean, and negotiations began at Paris, Vienna, and Madrid. The outcome of these conferences was an agreement between England and France to effect the exchange of Sardinia and Sicily just mentioned, recompensing Spain by giving her Parma and Tuscany in northern Italy, and stipulating that the emperor should renounce forever his absurd but irritating claim to the Spanish crown. This arrangement was to be enforced by arms, if necessary. The emperor at first refused consent; but the increasing greatness of Alberoni's preparations at last decided him to accept so advantageous an offer, and the accession of Holland to the compact gave it the historical title of the Quadruple Alliance. Spain was obstinate; and it is significant of Alberoni's achievements in developing her power, and the eagerness, not to say anxiety, of George I., that the offer was made to purchase her consent by ceding Gibraltar. If the Regent Orleans knew this, it would partly justify his forwarding the negotiations. Alberoni tried to back up his military power by diplomatic efforts extending all over Europe. Russia and Sweden were brought together in a project for invading England in the interest of the Stuarts; the signing of the Quadruple Alliance in Holland was delayed by his agents; a conspiracy was started in France against the regent; the Turks were stirred up against the emperor; discontent was fomented throughout Great Britain; and an attempt was made to gain over the Duke of Savoy, outraged by being deprived of Sicily. On the 1st of July, 1718, a Spanish army of thirty thousand troops, escorted by twenty-two ships-of-the-line, appeared at Palermo. The troops of Savoy evacuated the city and pretty nearly the whole island, resistance being concentrated in the citadel of Messina. Anxiety was felt in Naples itself, until the English admiral, Byng,[80] anchored there the day after the investment of Messina. The King of Sicily having now consented to the terms of the Quadruple Alliance, Byng received on board two thousand Austrian troops to be landed at Messina. When he appeared before the place, finding it besieged, he wrote to the Spanish general suggesting a suspension of arms for two months. This was of course refused; so the Austrians were landed again at Reggio, in Italy, and Byng passed through the Straits of Messina to seek the Spanish fleet, which had gone to the southward.