Can poor countries fight a just war to enforce global distributive justice? This dissertation applies just war theory to explore the conditions in which such a war is morally permitted. I argue that global justice should aim at meeting people's basic needs by promoting economic development of poor countries. This demand for global justice is triggered by the fact that the state system, sustained by coercion, influences people's life prospects profoundly and pervasively. When the rich and high income countries fail to discharge their duties, assigned by what I call The Commission of Development Aid, to assist poor countries' economic developments, their failure constitutes a just cause of war. When waging war for global justice, poor countries should have the right intention to observe all requirements of jus ad bellum and jus in bello. Only legitimate governments of poor countries have the legitimate authority to wage this war because of their legitimate authority to distribute resources in the domestic realm. A war for global justice should receive authorization from the Security Council or, at least, from the General Assembly. Finally, war for global justice does not necessarily fail to satisfy the requirements of reasonable chance of success, last resort, and proportionality.