Demetrios I Poliorketes was the son of one of Alexander's greatest generals, Antigonos I Monophthalmos. Antigonos was arguably the strongest of Alexander’s followers, the diadochs, at one time ruling over all of Alexander's eastern territories from Asia Minor to Baktria, except for Egypt.
Antigonos’ success led him to be the first diadoch to crown himself king, in 306 BC. By that time, Demetrios was an active participant in his father's wars, and was also crowned king along with his father.
Fearing Antigonos’ growing power, other diadochs allied themselves against him, and finally defeated and killed him at the battle of Ipsos in 301 BC. Following Ipsos, Demetrios continued to battle the other diadochs, and although he won numerous victories, he was usually unable to maintain his control over his conquests afterward.
His epithet, Poliorketes ('besieger of cities') was earned following his siege of Rhodes. While that siege ultimately failed, it featured a number of elaborate siege engines which had become a hallmark of Demetrios' style of warfare. Demetrios was eventually abandoned by his army, and he subsequently surrendered to Seleukos I of Syria in 288 BC. Demetrios died in captivity five years later.