After the Fourth Crusade broke Constantinople apart in 1204, the Peloponnese changed hands rapidly. The Frankish crusaders swept in first, but by 1206 or 1207 a Venetian fleet under Premarini — sailing with a son of the legendary Doge Enrico Dandolo — seized the Messenian peninsula and planted the Lion of Saint Mark over Koroni and Methoni. The Treaty of Sapienza in June 1209 formalized the arrangement: Venice got its two fortresses on the Greek mainland, and the Frankish Prince of Achaea got a neighbor he could not challenge.

For the Republic, the strategic logic was irresistible. Koroni sat at the hinge between the Adriatic and the Aegean, between Western Europe and the Levantine trade routes that made Venice rich. Every galley heading east stopped here. Every fleet heading west passed through. When the two fortress captains were increased to three in the late 13th century, two of them were posted at Koroni — the more important of the pair. In emergencies, a bailo arrived as an extraordinary consul, Venice's highest diplomatic rank. The town became a seat of Latin bishops, and merchants from across the Republic settled in to handle its famous crimson trade.

The mid-14th century brought the Black Death to Koroni and Methoni so severely that Venice had to ship a fresh wave of colonists from home to repopulate them. The franchise was extended broadly to encourage settlement — to everyone except the Jewish community. Out of crisis came bureaucracy: the metropolitan government issued a series of minutely detailed Statutes and Capitulations governing life in the fortress towns. One clause, in its small way revealing, forbade the Venetian garrison from wearing beards, so that they could be distinguished from the local Greek population.

The Venetians permitted Greek Orthodox bishops to reside alongside their Catholic counterparts — unusual among the Latin rulers of Greece — but the arrangement was uneasy. Reports from the latter half of the 14th century describe mistreatment of the Greek population severe enough that some fled Venetian territory for the Frankish-controlled areas of Achaea. By the early 15th century, as the Principality of Achaea collapsed, Venice expanded aggressively into the region: Navarino in 1417, six more castles by 1439. The boundary with Ottoman territory grew steadily closer. The first Ottoman naval attack on Koroni came in 1428. In 1500, during the Second Ottoman-Venetian War, Sultan Bayezid II stormed neighboring Methoni, and Koroni surrendered on 15 or 17 August of that year — ending nearly three centuries of Venetian rule.

The Ottoman period brought a different kind of history to Koroni. But it was not to last unchallenged. In 1532, supported by the local population, the Genoese admiral Andrea Doria retook the town for the Habsburg Emperor Charles V. The following spring, Ottoman forces besieged it again. Doria managed to relieve the town that summer, a naval victory that humiliated Suleyman the Magnificent enough that the sultan called in the corsair Hayreddin Barbarossa to finish the job.

Barbarossa had two unexpected allies: plague broke out among the Spanish garrison, and the winter of 1533-1534 proved savage. In April 1534, the garrison surrendered and sailed for Italy. The Albanian and Greek populations of Koroni who had joined Doria's cause left with him and eventually settled in southern Italy — founding communities including San Chirico Nuovo, Ginestra, and Maschito in the Kingdom of Naples, where the Arbëreshë dialect of Albanian is still spoken today. A piece of Koroni, in other words, persists in the Italian south.

The town returned to Ottoman administration, organized as part of the Sanjak of Methoni. Its annual revenue — 162,081 akçes — was granted to the endowment of Mecca. By 1582, the fortress held 300 Christian and 10 Jewish households; the Muslim population was confined to officials and a garrison of roughly 300 soldiers.

Koroni's modern story has a surprising chapter. Between 1966 and 1989, a facility for launching sounding rockets operated near the town. The first launches took place on 20 May 1966, timed to investigate an annular solar eclipse; those early rockets reached an altitude of 114 kilometers. From 1972 to 1989, Soviet-built M-100 meteorological rockets were launched from the site, reaching up to 95 kilometers. In total, 371 rockets were fired skyward from a hillside overlooking the Gulf of Messinia — a detail that would have baffled the Venetian captains who once surveyed these same waters looking for Ottoman sails.

Today Koroni is a town of about 1,200 people, part of the municipality of Pylos-Nestor since the 2011 government reform. The castle walls still stand above the whitewashed houses and the harbor. Olive oil and silk once moved through this port; now fishing boats bob where galleys once anchored. The eyes of the Republic are closed, but the view from the walls — out over the blue sweep of the Gulf — has not changed.