This research guide explains how patent owners and accused infringers plan, sequence, and fight patent disputes across many countries at once, when a single global product line reads on parallel patents in every major market. It starts from the governing principle of territoriality and the treaty scaffolding (Paris Convention priority, the PCT, and the European Patent Convention) that turns one invention into a worldwide portfolio, then compares the principal forums: U.S. district courts and the International Trade Commission, the Unified Patent Court, Germany's bifurcated system, the United Kingdom, China, Japan, and Korea. It analyzes the standard-essential patent and FRAND wars in depth, including the Huawei v. ZTE protocol, global rate-setting in Unwired Planet and InterDigital, the German Sisvel v. Haier willing-licensee line, and the anti-suit/anti-anti-suit injunction arms race. It also covers cross-border discovery and service (28 U.S.C. 1782, the Hague Evidence and Service Conventions, and the Aerospatiale comity test), the coordination of parallel proceedings and global settlements, and the recognition and enforcement of judgments abroad. Throughout, invented but clearly labeled hypotheticals ground the doctrine in concrete strategy for both sides.