The first Anglo-Japanese Alliance was signed on January 30, 1902, in London. This landmark agreement was forged between Great Britain and Japan, fundamentally altering the balance of power in East Asia. The primary motivation behind the alliance was to counteract the expansionist policies of Russia, especially in light of the Russo-Japanese War that would follow shortly after. The alliance committed both nations to mutual defense, marking Japan's emergence as a modern industrial power while enhancing Britain's interests in Asia.

Negotiations for the alliance began in 1901, spearheaded by the Japanese ambassador to Britain, Count Sato, and the British Foreign Secretary, Lord Lansdowne. The agreement was notable for acknowledging Japan's status as an equal power in the global arena. Under this alliance, both countries pledged to assist each other in case of war with a third power, positioning themselves strategically against Russian influences in Manchuria and Korea.

The alliance not only strengthened bilateral ties but also represented a significant shift in global diplomacy, introducing a new dynamic in the balance of power involving Asian nations. The public announcement of the alliance was met with optimism in Japan, as it elevated the nation's standing internationally and fostered a sense of nationalism and pride in its military capabilities.