Book excerpt: Napoleon's official diplomatic career lasted nearly two decades and involved relations with scores of kings, queens, ministers, diplomats, and secret agents across Europe and beyond. All those involved asserted their respective state (and often their private) interests across the entire span of international relations in which conflicts over trade and marriage were often inseparable from war and peace. For Napoleon, war and diplomacy were inseparable and complementary for victory. Much of Napoleon's military success was built upon a foundation of alliances and treaties. Although not always at war, Napoleon incessantly practiced diplomacy on a steady stream of international issues.