Larry, it has been too long since the 1st of June when you posted this excellent question, and I have to be the first to admit that I have not come across any declassified documents suggesting that the Japanese military or the Army hand-picked cabinet members submitted an official declaration of war to the League of Nations. However, some public articles have commented on what I consider to be a close approximation to an "answer". Therefore, I will try here...
I. The 20th Century: conflict, attitude and changing religions, by Frank E. Smitha. Copyright © 1998, 1999, chapter 27:
"In March 1940, Japan's parliament, the Diet, unanimously passed a declaration of support for holy war against China, and in the spring of 1940 the Japanese launched a new offensive there..."
II. From: Congressional Investigation into the Pearl Harbor Attack, Pt. 18 (Exhibits of the Joint Committee), pp. 2945-2946.
"ON THE DECLARATION OF WAR AGAINST THE UNITED STATES AND GREAT BRITAIN MEETING OF PRIVY COUNCIL DEC. 8, 1941"; written by Matsumoto-Head of Treaty Bureau.
"Advisor Ishii-At what time will war be declared? It is necessary to make sure that America and Britain don't saddle us with the responsibility. Premier-We hope for an immediate declaration.
[page 2] Advisor Kubota-A state of war already exists, but what is the viewpoint of the Imperial Headquarters..."
III. JAPAN ECHO Vol. 25, No. 4, August 1998; "Japanese Textbook Treatment of the Nanking Massacre";
"The Start of the Sino-Japanese War" (p. 254): Having brought Manchuria under its control, Japan advanced into northern China. The Sino-Japanese War began on July 7, 1937 (Shôwa 12), with the Marco Polo Bridge Incident, a clash between Japanese and Chinese armed forces at the Marco Polo Bridge on the outskirts of Peking (Beijing), without any declaration of war being issued. The fighting spread from northern China into central China, and at the end of the year the Japanese Army occupied the capital Nanking (Nanjing). In the process it killed an estimated 200,000 people, including women and children (the Great Nanking Massacre)..."
IV. A Declaration to the Japanese Government and the Japanese People; by Ignatius Ding; 06/25/95, 1995; Global Alliance for Preserving the History of World War II in Asia; P.O. Box 2066, Cupertino, CA 95015-2066.
"We, the people of Chinese descent worldwide, call on the Japanese government and its people to resolve the issue of its war responsibility. Until this is done, the Chinese people, as well as other Asian people, will be hard put to believe in Japan's commitment to peace...We urge the Japanese people of conscience to press the Japanese Government to immediately address the long overdue issues of war responsibility and reparation to Asian victims..."
MY COMMENTS: It appears that to many Chinese-Americans and Chinese nationalists of Taiwan and PRC agree on one point in that Japan has never absolved its war of aggression against the Chinese peoples. Since 15 August 1914, when Japan submitted its ultimatum to Germany, the Japanese government considered its responsibility to guard the territory of Kiaochau, the coastline of China, including the seas surrounding China and Japan against any hostile aggressors and all white entrenchments into Asia- whether for capitalist reasons or spreading the Christian word.
V. Japan: History: Modern Period;
"...Extremists exploited the situation, and the military
clique seized the opportunity offered them by the confusion of the times. The influence of the political parties steadily declined. After the Lugouqiao Incident led to the outbreak of war with China, the parties were forced to unite on a single platform of cooperation in the war effort. They were finally dissolved, and in their place was erected a united national party. With the Diet's functions reduced to little more than those of a rubber stamp, there could be no parliamentary obstruction to the tide of events that finally led to the outbreak of the Pacific War in 1941..."
MY COMMENT: Still no dates for a Japanese clique/cabinet/parliamentary declaration of war against the Chinese people. To gain power for his own selfish ambitions at the cost of Chinese autonomy, Yuan Shih-kai opened the door for Japan's military and police authorities with his quick acceptance of 'The Twenty-one Demands' on his own government. These Demands were presented by the Japanese imperialists on 18 January 1915. On 7 May 1915, they sent an ultimatum demanding a reply within forty-eight hours. The demands were divided into five parts. The first four contained the following: to transfer to Japan the rights Germany had seized in Shantung and to grant Japan additional rights in the province; to grant rights to the Japanese to lease or own land in southern Manchuria and eastern Mongolia and to establish residence, engage in industry and commerce, and have exclusive railway building and mining rights there; to reorganize the Han-Yeh-Ping Iron and Steel Company as a joint Sino-Japanese enterprise; and to undertake not to lease or cede any harbours or islands along China's coastline to any third power. The fifth part contained demands that Japan should control China's political, financial, military and police affairs and should build vital railway lines connecting the provinces of Hupeh, Kiangsi and Kwangeung. Yuan Shih-kai accepted all the demands except those in the fifth part, about which he pleaded for 'further negotiations'. Thanks to the unanimous opposition of the Chinese people, Japan failed to get her demands implemented."
VI. "The China War"; dissertation; by Theodore F. Cook, Jr.; Ph.D.; Professor of History at William Paterson University; January 2000.
MY COMMENT: "Theodore F. Cook, Jr., Ph.D., stated in his 'The China War', that China had been at war with Japan for eight years (July 1937 through August 1945) with heavy fighting that actually began with the Manchurian seizure of 1931."
In retrospect, many Japanese nationalists and scholars focusing on how to conceive the "Sino-Japanese War" (1931 - 1945) have used the term "fifteen year war", although it was slightly less than fourteen years from the Manchurian Incident of 18 September 1931 until the end of the war in August 1945.
On the other hand, many Chinese-Americans and Taiwanese have used the term "the war of resistance against Japan" to describe the war from their perspective. The westerners tend to see these events as part of World War II; Americans and some Japanese have tended to focus on the "Asia-Pacific War". Some have used the term, "The second Sino-Japanese war," but in general it was felt that "The Sino-Japanese War, 1931-1945" is a neutral comprehensive term that describes our subject matter and is acceptable to all sides.
Therefore, with the above references, I conclude that Japan acted in warlike aggression against the Chinese peoples starting 1931 (exact date to commence with the seizure of Manchuria- 18 September 1931). However, I was unable to locate a public document or article that described Japan having declared war on China through a political or Army process at a particular clique/ cabinet/ parliamentary meeting.