Overview

This 1937 booklet analyzes the Sino-Japanese conflict that began in July 1937 (the Marco Polo Bridge Incident) through the lens of international law, especially focusing on the concept of an “undeclared war.” Lin’s central argument is that Japan’s military actions against China violated multiple international treaties and norms, including the League of Nations Covenant, the Nine-Power Treaty, and the Kellogg-Briand Pact (Pact of Paris). The study presents a legal case identifying Japan as an aggressor and condemns its conduct in land, sea, and air warfare as contrary to humanitarian law.

Part I — The Nature of the Undeclared War

1. War in International Law

Lin traces how the right to make war—once considered a sovereign prerogative—was progressively restricted after World War I:

• The League of Nations Covenant established war as a matter of collective concern.

• The Nine-Power Treaty (1922) obligated signatories, including Japan, to respect China’s sovereignty and integrity.

• The Kellogg-Briand Pact (1928) outlawed war as a tool of national policy, binding both Japan and China to seek peaceful resolution of disputes.

Lin concludes that Japan’s attack on China was illegal under all these agreements and therefore a violation of international law.

2. Self-Defence

While international law recognizes the inherent right of self-defence, Lin argues Japan’s actions cannot be justified under this doctrine. The right is not absolute and must be subject to international scrutiny, not unilateral declaration. Citing scholars like Quincy Wright and Lassa Oppenheim, Lin insists that Japan’s claim of acting in self-defence is invalid, as its acts far exceeded any legitimate defensive measures.

3. The Case of Manchuria (1931–32)

Lin reviews Japan’s occupation of Manchuria and the creation of the puppet state “Manchukuo.” The Lytton Report (1932) and the League of Nations concluded these acts were not measures of self-defence but aggression, violating both the Nine-Power Treaty and the Pact of Paris. The doctrine of non-recognition, adopted by the U.S. and League members, established that no state would recognize territorial gains made by force.

4. The Present Case (1937 War)

Japan’s escalation after the Lukouchiao (Marco Polo Bridge) and Hungjao (Shanghai) incidents is examined. Lin notes:

• Japan’s official justification—that it was combating anti-Japanese movements led by Chiang Kai-shek—is a pretext for imperial expansion.

• The League of Nations Assembly (October 1937) and the U.S. government both declared Japan’s actions inconsistent with international law, the Nine-Power Treaty, and the Kellogg-Briand Pact.

• Lin thus characterizes Japan’s campaign as unlawful external aggression, not legitimate self-defence.

5. Legal War vs. Material War

Because neither Japan nor China formally declared war, the conflict was a “material” (de facto) war but not a “legal” (de jure) war. Lin notes, however, that the absence of a declaration does not negate the applicability of international law—the laws and customs of war still apply.

Part II — Rules and Customs of Warfare

Lin details how Japan violated the established laws of war on land, sea, and in the air.

1. Land Warfare

• Treatment of Combatants: Japan’s General Katsuki announced that no quarter would be given—violating the Hague Regulations that guarantee humane treatment of prisoners.

• Treatment of Non-Combatants: Reports of massacres (e.g., Yangchang and Huangsha) illustrate Japanese disregard for civilian protection.

• Use of Poison Gas: Citing medical evidence from Dr. E. F. Ettinger and Dr. Borie of the Nanking Red Cross, Lin accuses Japan of using mustard gas in North China and Shanghai, breaching the 1925 Geneva Gas Protocol.

2. Maritime Warfare

Japan’s naval attacks on Chinese fishing junks near Hong Kong are presented as clear violations of maritime law and humanitarian principles, since coast-fishing vessels are protected under Hague Convention XI (1907). Over 300 civilians—men, women, and children—were reported killed in these attacks.

3. Aerial Warfare

Lin gives extensive attention to Japan’s bombing campaigns, arguing that they contravene both legal codes and moral norms:

• Indiscriminate Bombing: Cities such as Nanking, Canton, and Hankow were bombed despite having no significant military targets.

• Civilian Casualties: Reports describe thousands of non-combatant deaths; Lin cites Western journalists and the League of Nations’ condemnation.

• Attacks on Hospitals and the Red Cross: The Nanking Central Hospital was bombed, killing 150 patients despite displaying the Red Cross symbol.

• Destruction of Cultural Monuments: Japanese forces destroyed or damaged major universities (Nankai, Central, Fudan, Sun Yat-sen, etc.) and heritage sites (Temple of Heaven, Summer Palace), which Lin sees as an attempt to eradicate Chinese culture.

• Neutral Lives and Property: Japanese aircraft attacked British diplomatic vehicles and endangered American citizens, prompting protests from multiple governments.

4. The Verdict of the World

On September 28, 1937, the League Assembly unanimously condemned Japan’s aerial bombardments as acts of barbarism with “no excuse” under international law. Lin ends by quoting President Franklin D. Roosevelt’s “Quarantine Speech” (October 5, 1937), interpreting it as a moral appeal for the restoration of international order and the sanctity of treaties.

Conclusion

Lin concludes that the Sino-Japanese conflict, though undeclared, constitutes an illegal war of aggression violating both the spirit and the letter of modern international law. He positions China as a victim of aggression and Japan as a violator of the moral and legal order established after World War I. The study also functions as an early legal and moral indictment of total war tactics, anticipating later war-crimes discourse.

Appendix (p. 24)

The final page lists other publications by the China Institute in America, including essays on Manchuria, Chinese economic emergence, and cultural studies, indicating the broader mission of the Institute to promote understanding of modern China.