Final answer:
Otto von Bismarck is considered the architect of the alliance system of countries before World War I.
Step-by-step explanation:
The architect of the alliance system of countries that existed before World War I was Otto von Bismarck. Bismarck, the German chancellor, pursued conservative policies to strengthen Prussia and Germany. He developed a series of alliances, such as the Triple Alliance with Austria-Hungary and Italy, to check the power of Russia and France and prevent them from posing a threat to German leadership in the region.