Who was the most successful country during war?

Determining the "most successful" country during war can vary depending on the criteria used, such as military victories, territorial gains, or long-term impacts. Historically, the British Empire was highly successful in the 19th and early 20th centuries, expanding its territory through various conflicts. In World War II, the Allied powers, particularly the United States and the Soviet Union, emerged as significant victors, leading to a reshaping of global power dynamics. Ultimately, success in war is often subjective and context-dependent.