What was the bismarckian system of alliances, and how successful was it at keeping the peace? what issues lay behind the international crisis that europe faced in the late 19th and early 20th centuries?

The Dual Alliance was a defensive alliance between Germany and Austria-Hungary, which was created by treaty on 7 October 1879 as part of Bismarck's system of alliances to prevent or limit war. The two powers promised each other support in case of attack by Russia. Also, each state promised benevolent neutrality to the other if one of them was attacked by another European power (generally taken to be France, even more so after the Franco-Russian Alliance of 1894). Germany's Otto von Bismarck saw the alliance as a way to prevent the isolation of the German Empire, which had just been founded a few years before, and to preserve peace, as Russia would not wage war against both empires

The Bismarckian system of alliances was a system of alliances between nations. Its purpose was to preserve peace and a status quo. It was successful until William the 2nd dismissed it. In general what really brought about WWI was the decisions that were made by European leaders that affected militarism and nationalism as well as the leaders desire to stifle internal decent.