This enabled contacts with the interior that no people, including Africans themselves, had ever established before. Steam iron ships also played a vital role in European penetration into China. Western armament continued to increase. In the late 19th century, Western soldiers were armed with repeating rifles. Representing a huge advantage. Advances from the Industrial Revolution took place, including technology, but also better health care and increased literacy. This created the impression that the West was superior to the rest of the world. Attempts at western expansion took place starting with the Crusades. Economic motivations also contributed. For most of the 19th century, African history was marked by significant economic innovation and change. In the northern region, below the Sahara Desert, Islam continued to spread, thanks to the holy war movement that 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 favored by Western imperialism. Islam has become an integral part of many African cultures and traditions. Africans faced an economic challenge. With the advent of the Atlantic slave trade and the changing balance of trade, it became much more difficult to obtain goods, such as weapons. Many African leaders have worked hard to find alternative ways to import and export goods. As a result, they increased internal slavery in order to provide cheap labor. Conditions for women worsened as slavery expanded. In West Africa, imperialism increased as Britain and France acquired new port territories. A small number of African territories eventually converted to Christianity and upheld Western values. Both states, Liberia and Sierra Leone, were formed by freed slaves. The freed slaves formed a