Even before Japanese troops arrived in Indochina, Tokyo had already opened another front: the airwaves. Every evening, French-language broadcasts transmitted from Japan traveled thousands of kilometers to France, North Africa, and especially French Indochina. Behind these seemingly cultural or informative programs was, in reality, a full-scale psychological war. For Imperial Japan, radio was meant to prepare minds long before armies entered the field. Today, this battle of the airwaves has largely been forgotten.

Radio : Japan’s New Instrument of Power

In the early 1930s, Japan quickly understood the strategic value of international broadcasting. The overseas service of NHK, soon nicknamed “Radio Tokyo” by foreign listeners, was given a clear mission: defend Japanese policy abroad and influence international public opinion.

Among the languages selected for these international broadcasts, French occupied a special place. This was no coincidence. At the time, French remained one of the world’s major diplomatic languages, but above all the language of a vast colonial empire. Internal Japanese broadcasting documents explicitly stated the objectives: the programs were intended to reach “France, North Africa, and Indochina.” The latter rapidly became a priority target.

Why Indochina Interested Tokyo

For Imperial Japan, French Indochina represented far more than a distant colonial territory. The region held major strategic importance because it provided access to southern China, Southeast Asian maritime routes, and the region’s natural resources. But Indochina also had symbolic value. Tokyo sought to weaken the prestige of European colonial powers in Asia and present itself as the defender of “Asia for the Asians.”

Radio therefore became an ideal tool. French-language broadcasts directly targeted colonial elites: administrators, military officers, teachers, journalists, and French-speaking merchants. By speaking their language, Radio Tokyo aimed to penetrate the very heart of the French colonial system. Behind the microphone, nothing was left to chance. Long before Japan officially entered the war, content was closely supervised by military authorities. Radio gradually evolved from a simple broadcasting medium into a political weapon.

In 1937, some French-language broadcasts aimed at Indochina were aired daily around 7 p.m. Indochina local time on shortwave frequencies:

JZK: 15.160 kc (19.79 m) – JZJ: 11.800 kc (25.42 m)

These frequencies allowed transmissions over extremely long distances and reached colonial listeners equipped with shortwave radios.

December 1941: Propaganda Expands

After the attack on Pearl Harbor in December 1941, Radio Tokyo became fully integrated into Japan’s wartime propaganda machine. International broadcasting expanded to more than thirty hours daily in around twenty languages. French retained an important role within transmissions aimed at Europe and the French colonies.

The objectives were now openly acknowledged : weaken the Allies, create divisions within colonial empires, promote the “Greater East Asia Co-Prosperity Sphere” led by Japan. Indochina then became a central theme in French-language broadcasts.

“Liberating” Asia Through the Airwaves

The message broadcast by Radio Tokyo followed a consistent line. France was portrayed as a weakened and outdated colonial power. Its empire was described as unjust and doomed to disappear. In contrast, Japan claimed to champion the emancipation of Asian peoples.

The vocabulary was carefully chosen: cooperation, protection, Asian revival, emancipation. The word “occupation” was carefully avoided. This rhetoric specifically targeted Indochina, portrayed as a territory destined to leave the European colonial orbit and join the new Asian order envisioned by Tokyo.

Radio Saigon Under Japanese Oversight

On the ground, the situation became increasingly complex as the Japanese presence expanded in Indochina. Local French authorities, still loyal to the Vichy regime, sought above all to preserve colonial order by cooperating with the Japanese. This collaboration also affected radio broadcasting.

Special Radio Tokyo programs were relayed by Radio Saigon. Other broadcasts were produced locally under agreements concluded between French and Japanese authorities.

An agreement signed in June 1943 officially reorganized broadcasting in Indochina. French technicians remained in place, but editorial control gradually came under Japanese supervision. Japanese authorities also paid particular attention to Vietnamese announcers employed for local broadcasts. Japanese radio archives emphasized their strategic importance while stressing the need to monitor their loyalty. Radio had become a genuine tool of political and psychological control.

“These individuals, originating from the target countries, bring indispensable authenticity to the broadcasts. However, their recruitment poses particular difficulties: their loyalty must be verified, their training ensured, and their supervision constant. Because of these challenges, the number of announcers in the Annamese language remains limited, but their impact on Vietnamese listeners is considered considerable.”
Radio Yearbook of Japan, 1943

Vietnamese Broadcasts from Taiwan

Japanese propaganda aimed at Indochina did not rely solely on French. Beginning on December 1, 1939, Radio Taipei (Taiwan Hoso Kyokai), broadcasting from Taiwan (then called Formosa in French), also aired Vietnamese-language programs directed toward French Indochina.

Thanks to its geographical proximity to Vietnam and a 10 kW transmitter, the station played a key role in Japan’s regional broadcasting network. The programs promoted the same themes: denunciation of Western colonialism, Asian unity, cooperation with Japan, and the construction of “Greater East Asia.”

Broadcasts were transmitted in several languages (Vietnamese, English, Cantonese, Hokkien, and Malay) in order to reach highly diverse audiences across Southeast Asia.

“The content emphasized: calls for cooperation with Japan for a new era in Asia, the liberation of Asia by Japan, the construction of the Greater East Asia Co-Prosperity Sphere, and denunciation of Western colonialism,”
noted the Radio Yearbook of Japan in 1943.

Psychological Warfare Before Occupation

As Japanese forces gradually established themselves in Indochina, radio took on yet another role. It no longer served merely to influence public opinion. It now had to justify Japan’s physical presence on the ground.

Broadcasts explained why Japanese intervention was supposedly necessary, even beneficial. Indochina was described as a territory in transition, destined to leave French domination and join the Asian sphere led by Tokyo.

One recurring problem for Japanese propagandists, however, was the French pronunciation of Radio Tokyo’s announcers, which often led to amusing misunderstandings and mockery among French-speaking listeners in colonial Indochina.

September 1945: The End of Tokyo’s Foreign Voices

Until the final months of the war, Indochina remained a constant topic in Radio Tokyo’s French-language broadcasts. Even after Japan’s surrender in August 1945, some foreign-language transmissions briefly continued amid widespread confusion.

General Douglas MacArthur, Supreme Commander of the Allied Forces in Japan, finally ordered the shutdown of all foreign-language broadcasts on September 4, 1945.

Radio Tokyo then permanently ceased speaking French. With it disappeared one of the least-known episodes of the battle of the airwaves in Asia.

Tokyo Radio Broadcast Schedule

(Indochina Time)

Language Color Codes

• 🟦 English
• 🟥 French
• 🟩 Japanese
• 🟪 German / Cantonese / Fukien
• 🟧 Italian
• 🟨 Spanish
• 🟫 Mandarin Chinese
• ⚫ Thai / Burmese / Hindustani / Arabic / Malay / Dutch
• ⚪ Music / General Programming

Main Stations and Frequencies

Stations may carry different programming depending on the hour and language service.

Morning Schedule (02:00 – 09:30)

Afternoon Schedule (10:30 – 15:00)

Evening and Night Schedule (17:00 – 01:30)

Radio Taipei Programs (1943)