日本官方文件显示，日本从1885年开始调查钓鱼岛到1895年正式窃占，始终是秘密进行的，从未公开宣示，因此进一步证明其对钓鱼岛的主权主张不具有国际法规定的效力。

　　(二)钓鱼岛随台湾岛被迫割让给日本

　　1895年4月17日，清朝在甲午战争中战败，被迫与日本签署不平等的《马关条约》，割让“台湾全岛及所有附属各岛屿”。钓鱼岛等作为台湾“附属岛屿”一并被割让给日本。1900年，日本将钓鱼岛改名为“尖阁列岛”。

Japan's official documents show that from the time of the facts-finding missions to Diaoyu Dao in 1885 to the occupation of the islands in 1895, Japan had consistently acted in secrecy without making its moves public. This further proves that Japan's claim of sovereignty over Diaoyu Dao does not have legal effect under international law.

2. Diaoyu Dao was ceded to Japan together with the Taiwan Island

On April 17, 1895, the Qing court was defeated in the Sino-Japanese War and forced to sign the unequal Treaty of Shimonoseki and cede to Japan "the island of Formosa (Taiwan), together with all islands appertaining or belonging to the said island of Formosa". The Diaoyu Dao Islands were ceded to Japan as "islands appertaining or belonging to the said island of Formosa". In 1900, Japan changed the name of Diaoyu Dao to "Senkaku Islands".

　　三、美日对钓鱼岛私相授受非法无效

　　第二次世界大战后，钓鱼岛回归中国。但20世纪50年代，美国擅自将钓鱼岛纳入其托管范围，70年代美国将钓鱼岛“施政权”“归还”日本。美日对钓鱼岛进行私相授受，严重侵犯了中国的领土主权，是非法的、无效的，没有也不能改变钓鱼岛属于中国的事实。

　　(一)“二战”后钓鱼岛归还中国

III. Backroom Deals Between the United States and Japan Concerning Diaoyu Dao are Illegal and Invalid

Diaoyu Dao was returned to China after the Second World War. However, the United States arbitrarily included Diaoyu Dao under its trusteeship in the 1950s and "returned" the "power of administration" over Diaoyu Dao to Japan in the 1970s. The backroom deals between the United States and Japan concerning Diaoyu Dao are acts of grave violation of China's territorial sovereignty. They are illegal and invalid. They have not and cannot change the fact that Diaoyu Dao belongs to China.

1. Diaoyu Dao was returned to China after the Second World War