This paper provides general approaches to “contractual breach” in four countries: France, Germany, China, the USA in the first chapter. The thesis then summarizes important viewpoints in order to comprehend the genuine intentions of the delegates who authored Article 25 of the CISG before delving into the analysis of the fundamental breach aspects. Next, the author examines the elements of fundamental breach and clarifies its requirements through rules applied to the comprehension of the CISG under Article 8 and 9. In closing, according to recent court decisions, this thesis examines the application of Article 25 and provides global businesses with advice on pursuing international sales of goods contracts.