Aratus, a brilliant twenty-year-old guerrilla fighter with a hearty loathing for tyrants and Macedon alike, frees Sicyon from a tyranny in 251 and, after establishing a democracy, brings it into the Achaean League for defense against Macedonia.

The Romans attack Panormus after taking Kephalodon in 251 BCE.

After fierce fighting, the Carthaginians are defeated and the city falls.

With Panormus captured, much of western inland Sicily falls with it.

The cities of Ietas, Solous, Petra, and Tyndaris agree to peace with the Romans this same year.

Diodotus, a local Greco-Bactrian governor, declares the independence of the Afghan plain of the Amu River, in about 250 BCE.

Ptolemy reasserts his influence in the Aegean while the Macedonian forces are bogged down in Greece, making good the setback suffered during the Chremonidean War.

The Romans, shifting their attention to the southwest in 250, send a naval expedition toward Lilybaeum.

En route, the Romans seize and burn the Carthaginian holdout cities of Selinus and …

…Heraclea Minoa.

This expedition to Lilybaeum is not successful, but attacking the Carthaginian headquarters demonstrates Roman resolve to take all of Sicily.

The Carthaginians defeat the Roman fleet at Drepana, forcing the Romans to continue their attacks from land.

Roman forces at Lilybaeum are relieved, and Eryx, near Drepana, is seized, thus menacing that important city as well.

Halley's comet, which swings around the Sun once every seventy-six years, becomes known to astronomers in 240 BCE.

Its orbital period over the last three centuries has been between seventy-five and seventy-six years, though it has varied between seventy-four and seventy-nine years since its discovery.

The Qin state, centered in present Shaanxi (Shenxi), has emerged as the most powerful of the Warring Kingdoms.

The once-mighty Seleucid kingdom had in the beginning of the third century BCE begun to lose control over large territories.

Parthia, Bactria, and Sogdiana have by the middle of this century gained their independence.