He commanded the Genoese galleys near Cyprus in a war which the Genoese had with the Venetians.
Between the years 1461 and 1463 the Genoese were acting as allies with King John of Calabria, and Columbus had a command as captain in their navy at that time.
"In 1477," he says, in one of his letters, "in the month of February, I sailed more than a hundred leagues beyond Tile." By this he means Thule, or Iceland.

"Of this island the southern part is seventy-three degrees from the equator, not sixty-three degrees, as some geographers pretend." But here he was wrong.

The Southern part of Iceland is in the latitude of sixty-three and a half degrees.

"The English, chiefly those of Bristol, carry their merchandise, to this island, which is as large as England.

When I was there the sea was not frozen, but the tides there are so strong that they rise and fall twenty-six cubits." The order of his life, after his visit to Iceland, is better known.
He was no longer an adventurous sailor-boy, glad of any voyage which offered; he was a man thirty years of age or more.