This allowed contacts with the interior that no people, including Africans themselves, had ever achieved before. Steam-powered iron boats were also crucial to European penetration into China. Western armaments continued to increase. Towards the end of the 19th century, Western soldiers were armed with repeating rifles. Representing a huge advantage. There have been benefits from the Industrial Revolution, including not only technology, but also better healthcare and increased literacy. This gave the belief that the West was superior to the rest of the world. Attempts at Western expansion occurred from the Crusades onward. Economic reasons also contributed to this. During much of the 19th century, African history developed with significant innovations and economic changes. In the northern region, beneath the Sahara Desert, Islam continued to spread, through the holy war movement, which emerged in the late 18th century. Literature began to develop in the written language of East Africa, called Swahili. Later in the 19th century, the spread of Islam was aided by Western imperialism. Islam has become part of many African cultures and traditions. Africans faced the economic challenge. With the advent of the Atlantic slave trade and the shifting balance of trade, it became much more difficult to obtain goods, such as firearms. Many African leaders have worked hard to find alternative ways of importing and exporting goods. As a result, they increased domestic slavery as a means of providing cheap labor. Conditions for women worsened as the use of slaves expanded. In West Africa imperialism broke out most, as Britain and France acquired new port territories. A small number of African territories ended up converting to Christianity and supporting Western values. The two states, Liberia and Sierra Leone, were formed by freed slaves. The freed slaves formed a