He allowed the fleet, which his father had organized, to fall into decay; and the empire was thus less able than ever to resist the exacting demands of the rival powers of Venice and Genoa.
During his reign the Ottoman Turks under Osman conquered nearly the whole of Bithynia; and to resist them the emperor called in the aid of Roger de Flor, who commanded a body of Aragonese and Catalan adventurers known as Almogavares. The Turks were defeated, but Roger was found to be nearly as formidable an enemy to the imperial power. He was assassinated by Andronicus's son and colleague (sometimes referred to as emperor Michael IX, though he never ruled in his own name), in 1305. His adventurers (known as the Macedonia, conquered the Duchy of Athens and Thebes.
From 1320 onwards the emperor was engaged in war with his grandson Andronicus. He abdicated in 1328 and died in 1332.
John V was the father, with Helena, a daughter of John VI Cantacuzenus, of Andronicus IV Palaeologus and Manuel IIPalaeologus.
AndronicusII married firstly Anna of Hungary and fathered Michael Palaeologus, who predeceased his father but was a co-regent, as such sometimes numbered the ninth.
Manuel II married a daughter of a regional lord of the dissolved Serbian realm.