But this great success was balanced by the failure of the Greeks, under Ypsilanti, to capture Napoli di Romania,—­another strong fortress, defended by eight hundred guns, regarded as nearly impregnable, situated, like Gibraltar, on a great rock eight hundred feet high, the base of which was washed by the sea.  It was a rash enterprise, but came near being successful on account of the negligence of the garrison, which numbered only fifteen hundred men.  An escalade was attempted by Mavrokordatos, one of the heroic chieftains of the Greeks; but it was successfully repulsed, and the attacking generals with difficulty escaped to Argos.  The Greeks also met with a reverse on the peninsula of Cassandra, near Salonica, which proved another massacre.  Three thousand perished from Turkish scimitars, and ten thousand women and children were sold into slavery.

Thus ended the campaign of 1821, with mutual successes and losses, disgraced on both sides by treachery and massacres; but the Greeks were sufficiently emboldened to declare their independence, and form a constitution under Prince Mavrokordatos as president,—­a Chian by birth, who had been physician to the Sultan.  The seat of government was fixed at Corinth, whose fortress had been recovered from the Turks.  Seven hundred thousand people threw down the gauntlet to twenty-five millions, and defied their power.

The following year the Greek cause indirectly suffered a great blow by the capture and death of Ali Pasha.  This ambitious and daring rebel, from humble origin, had arisen, by energy, ability, and fraud, to a high command under the Sultan.  He became pasha of Thessaly; and having accumulated great riches by extortion and oppression, he bought the pashalic of Jannina, in one of the richest and most beautiful valleys of Epirus.  In the centre of a lake he built an impregnable fortress, collected a large body of Albanian troops, and soon became master of the whole province.  He preserved an apparent neutrality between the Sultan and the rebellious Greeks, whom, however, he secretly encouraged.  In his castle at Jannina he meditated extensive conquests and independence of the Porte.  At one time he had eighty thousand half-disciplined Albanians under his command.  The Sultan, at last suspecting his treachery, summoned him to Constantinople, and on his refusal to appear, denounced him as a rebel, and sent Chourchid Pasha, one of his ablest generals, with forty thousand troops, to subdue him.  This was no easy task; and for two years, before the Greek revolution broke out, Ali had maintained his independence.  At last he found himself besieged in his island castle, impregnable against assault, but short of provisions.  From this retreat he was decoyed by consummate art to the mainland, to meet the Turkish general, who promised an important command and a high rank in the Turkish service.  In the power now of the Turks, he was at once beheaded, and his head sent to Constantinople.