Why did European imperialism increase tensions between the Great Powers?

Fashoda Incident of 1898

British and French forces clashed in Sudan after a French expedition to the region. Both countries claimed the territory. The incident almost led to war between Britain and France until a compromise was reached in which France accepted British control of Egypt and Sudan and Britain French control of Morocco. 

Weltpolitik (1890-1914)

Wilhelm II became Kaiser of Germany and began a policy of Weltpolitik in which he aimed at gaining overseas possessions, such as colonies. They were a new Empire and their late entry to the arms race threatened Britain's strategic and commercial aims.

Naval Arms Race (1898-1912)

Germany began their naval programme, believing it was necessary to protect their trade and empire. They wanted to be respected by other nations and empires, believing that for this, they would need a powerful naval fleet. This worried other empires, so they too started to further develop their Navies.

Entente Cordiale (1904)

As they both felt threatened by German expansion and development, Britain and France signed the Entente Cordiale, which settled their rivalry and differences. The Kaiser believed that this new friendship threatened Germany's international influence, so he tried to destroy their friendly relationship. 

The Moroccan Crises (1905 and 1911)

In 1905, the Kaiser stated that Germany supported Moroccan independency to attempt to cause a split between Britain and France, however Britain continued to side with France, even when Germany sent a gunboat to the Moroccan region to undermine French power.