In view of her established supremacy at sea, England was generally regarded as the police-constable of Europe in naval affairs, and upon her fell the chief duty of chastening the Dey of Algiers, though on this occasion the Dutch Government also lent its assistance. Quite early in the spring of 1816, Lord Exmouth placed himself in communication with the Dey, and stated the terms of the British demands. These were that the Ionian Islands, long a hunting-ground for the Barbary pirates, should be henceforth treated as British territory; that the British Government should be accepted as arbitrator between the Barbary Powers and Naples and Sardinia, who had a long list of claims and grievances against them; and that the Barbary Powers should enter into a definite undertaking to abolish all slavery of Christians within their dominions, and to treat all prisoners of war, of whatever nation, in accordance with the customs of civilised nations. The Dey agreed to the first two demands and released the Ionian slaves as British subjects, but declined all promises as to the abolition of slavery. Leaving that matter in abeyance, Exmouth sailed on to Tripoli and Tunis, whose Deys he found more amenable to reason, and who consented to make declarations in the form demanded by the British Admiral upon all three points. Exmouth then returned to Gibraltar, where his squadron was assembled, and at once resumed negotiations with the Dey with the intention of procuring his adhesion to the all-important undertaking to abolish Christian slavery. The Dey, after many evasions, at length repeated his refusal on the ground that he was a subject or vassal of the Sultan, and could not consent to so important a stipulation without his authority. Exmouth granted a delay of three months accordingly, and himself lent a frigate, the _Tagus_, to convey the Dey's envoy to Constantinople.