In the 1300's Catholic Spain forced Jews to convert. Actually, there was a choice. You could convert, you could leave Spain, You and your entire family could be executed. Hundreds converted to Christianity. Hundreds were killed too. These converts became known as "New Christians" or "Conversos".
But some New Christians still practiced Judaism, in secret. The Kol Nidre prayer that starts Yom Kippur became popular as the prayer for forgiveness for the lies a Jew needed to say and do every day to live in Spain. The Kol Nidre prayer is actually much older than the 1300's but became prominent in the 1300-1400s.
In the late 1400's, Spain once again passed laws to expell or convert Jews. This is the start of the Spanish Inquisition, which despite what Monty Python says, was not funny. 3,000-5,000 people were killed for their faith during the Inquisition.
Depending on when and where you learned US History, who Columbus was will be different. He was a Spanish sailor (Not even close); He was an Italian Nobleman (Maybe, but probably not); He was an Italian merchant sailor (probably). Italian would be not quite right in any case. What is today Italy was a group of kingdoms in the 1400s. When Shakespeare talks about two lovers in Verona, Verona is a kingdom and a city. Today it is a city. Columbus was most likely from Genoa. Today a city, then a kingdom.
Columbus was in Spain. Spain was one of the European powers. THE place to be, if you were a ship captain. In the 1400s, spice merchant was where the big money was. Europe loved spices. They were exotic. They came from "the Orient" (present day India and China). Importing spices was dangerous and expensive. In the late 1400s in Europe, black pepper was worth more per ounce than gold. There were two paths for spices to get to Europe. the land route was to go through Istanbul, across Turkey, across Persia (present day Iran and Iraq), Central Asia, through present day Pakistan and Afghanistan, then through India to the spice farms and markets. This route took over a year in each direction. The land route was dangerous. There were weather issues. there were bandits as well as taxes from the various kingdoms along the route.
The sea route also took a year or more in each way. The route was to leave Spain, then sail around Africa, across the Indian Ocean to India. The ships left Europe so heavily loaded, they were barely above the surface of the water. They traded with the slave ports along Africa. Being a sailor on a spice ship paid very, very well. Two voyages could make someone enough money to retire for the rest of your life. But, each voyage was between two to three years. Also, about a third of sailors died on each voyage.
Unlike in most history books, the Spanish crown did not fund Columbus' voyage. Two Jewish merchants did. Perhaps they saw the economic value in the trip. Perhaps they were wanted to "help a fellow tribesman". One thing is for sure. Columbus' first report from the new world went to them, not the Queen.
The last day for Jews to legally live in Spain was August 2, 1492. August 2, 1492 corresponds with the Jewish Holiday of Tish B'Av. Tish B'Av commemorates the destruction of both the First (in 587 BCE) and Second (in 70 CE) Temples in Jerusalem. Tish B'Av is the saddest day in the Jewish year. The Temple in Jerusalem held the remains of the tablets of the Ten Commandments. Today the Temple is the sight of the Dome of the Rock and the Western Wall. Was this day chosen by the Spanish for its already sad history in Judaism? Don't know. Columbus was to sail on August 2. He sailed on August 3. Tish B'Av is a very, very dark day. Marriages are forbidden on it. It would be incredible bad luck for a ship to sail on Tish B'Av.
In Columbus' time most ship navigators were either Jewish or Muslim. Muslims had discovered mathematics. Jews had written the first navigation tables and created the first navigation tools. In the early 1400s European ships rarely left sight of land for the entire voyage around Africa. Imagine, being in the ocean. Only water to see and trying to get from A to B. Muslim and Jewish sailors could do it. They learned from more experienced sailors. They also started writing things down. By Columbus' time, most navigators were either Muslim or Jewish.
Ships sailed on the morning tide. The crew would board at sunrise and then set sail. For this voyage, Columbus had his crew board on the ships the night before. He then lifted anchor and moved from the docks and dropped anchor again. He and his crew were now no longer in Spain, but at sea and not subject to the expulsion order. Columbus' crew also had more Jews than normal on board. He had at least a dozen Jews out of a crew of about 90 on his three ships. Many of his key assistants were Jewish.
39 of Columbus' crew elected to say in what is now Cuba and not return to Spain. For a Spanish Jew, returning to Spain could mean being put to death by torture. Maybe the new land would be better.
For the next 200 or so years Spanish ships sailed to what is now Mexico, Central and South America. Many of these explorers and soldiers are suspected to be Conversos who may have left their life in hiding in Spain to live their faith in the Americas.
There is a custom of some Latinos of putting lit candles in the oven on Friday night. These are Catholic families. When asked, many say their mother and grandmother taught them to do it, that it is important, but not why. Perhaps, 400 years ago, their relative was a Conversos, a Jew in hiding celebrating the Sabbath. The blessings have been forgotten the ritual remains.