Yamamoto left Kobe port on 26 November 1937, at the time of the Japanese attack on Nanking from Shanghai, accompanied by a former diplomat named Shibasaki Michika.
The original plan was to visit about 14 countries in Europe, South America and the United States over a period of about eight months.
In reality, however, the voyage was extended to a year, until the ship returned to Yokohama on 29 November 1938. The number of countries visited increased to 16.
After this round-the-world trip, Yamamoto became increasingly ill from exhaustion and passed away about three years later. It was literally a "life-threatening" service trip.
On December 12, 1938, shortly after his return to Japan, Yamamoto gave a lecture on the results of his visit at the "Welcome Home Dinner for Catholic National Missions" held at Gakushi Kaikan in Kanda, Tokyo.
Yamamoto said:
"I was supported by the prayers of my friends and acquaintances around the world and was able to gain understanding of Japan in many countries."
He then reported on his achievements.
But he made little mention of how he had explained Japan's position on the Sino-Japanese war to the world. This may have been due to the fact that it was a diplomatic secret.
However, more than half a century later, in 1991, an American named Martin S. Quigley wrote a book titled 'Peace Without Hiroshima: Secret Action at the Vatican in the Spring of 1945` In the book, Yamamoto also makde clear Japan's position on the Japan-Sino War.
The author, Quigley, was an intelligence operative in the Office of Strategic Intelligence (OSS), which was part of the US Joint Chiefs of Staff.
In The Vatican Peace Mission, he vividly describes the peace mission from the US to Japan via the Vatican, which he himself was in charge of in 1945, near the end of the war. With its provocative subtitle, "Could Hiroshima Have Been Avoided?", the book had a profound impact on the Japanese people, and the story of the Vatican peace cable will be recounted in the next chapter.
As a Catholic himself, Quigley consulted a number of sources to find out what Japanese Catholics thought of the war before embarking on the peace process. He found a statement made by Shinjiro Yamamoto, "a particularly important figure among Japanese Catholics", to his friends in Rome at the beginning of 1938, while on a tour of the world.
"An armed conflict between Japan and the United States is inevitable. There is a racial conflict and a conflict of national interests involved. Japan is preparing for war. If it does, we can see that it will be a terrible war."
Quigley added
At the same time, ...... Yamamoto defended Japan's invasion of China (as described by Quigley) as follows.
That is
(1) This is a war against communism.
(2) This is a war to protect Japan's national interests.
(3) This is a war to suppress the anti-Japanese movement in China.
(4) This is a war to protect Japan's interests in North China and Manchuria.
From these arguments, Yamamoto concluded that the war was morally justified, writes Quigley. We don't know whether Yamamoto used this argument in every country and against every leader on his world tour. But there is no doubt that he proudly stated that the Japan-Sino War was not a war of aggression.
And Yamamoto believed that this position was "generally understood".
