Trade networks grew along the Silk Road, and economies got more modern. This meant that people required new means to manage their finances, such as credit systems. When Rome traded with India, it did well. It shipped gold, glass, and silver to India and got silk, spices, and colors back in return. It also traded with India via the Red Sea. Cities like Petra and Palmyra became important trading hubs. The Byzantine Empire played a vital role in trade, and Alexandria and Constantinople were significant endpoints on the Silk Road. Islam emerged in the seventh century, which facilitated trade by bringing together large areas under a single set of laws, norms, and economic systems. Baghdad became a significant trade center by introducing innovative concepts, including the issuance of letters of credit and the adoption of a single currency throughout the region. Trade was greatly affected by the Mongol invasions and the Crusades. In the 1500 s, the Ottoman Empire resumed its involvement in the Middle East. The Cairo Geniza papers reveal how Islamic law tried to be fair and open, which helped businesses grow. In medieval Europe, Jewish communities played a vital role in banking. Because of their religion, they could not charge interest, yet these improvements made international trade work for hundreds of years. Venice and Genoa taught the East and West how to trade with each other.