Step 1: Understanding the Concept:
The question asks to identify the leader who made military service mandatory to strengthen his nation's army.
Step 2: Detailed explanation:
Otto von Bismarck, as the Minister President of Prussia, was the architect of German unification. A key part of his strategy was to build a powerful and highly disciplined Prussian army. He, along with the War Minister Albrecht von Roon, implemented reforms that included universal military conscription for three years of service for all able-bodied men. This system of compulsory military service created a large, well-trained reserve force that proved crucial in the wars of German unification against Denmark, Austria, and France.
Step 3: Final Answer:
Bismarck introduced compulsory military service in Prussia.