This scenario is still at the brainstorming stage. I'm trying to decide whether or not to develop it into a full-scale scenario. 

What actually happened: In 1937, shortly after they took the Nationalist Chinese capital of Nanking, the Japanese aircraft attacked a US gunboat that was escorting two oil tankers away from the fighting. In a sustained attack by several planes, the Japanese sunk the Panay, and destroyed the two oil tankers. The attacks had to have been deliberate. The gunboat was clearly marked as American, and the Japanese planes came in very low several times in the course of the attack. Several Americans were killed in the attack, but some survived, including a film crew which got footage of most of the attack. The Japanese later apologized and said that the sinking had been accidental, a case of mistaken identity. 

The Roosevelt administration talked the cameramen into withholding the crucial footage where the Japanese planes swooped down low enough that they could not have missed the fact that this was an American ship. The rest of the footage was shown in movie theatres across the country. Roosevelt was afraid that showing the entire footage would generate a war fever and tie his hands in dealing with the Japanese. Instead, he found that the truncated film had very little impact on the isolationist mood of the country and in Congress. One congressional leader told him that he could bring a declaration of war to congress, but he would find essentially no support for it there. 

The Japanese had committed an act of war against the US and suffered no adverse consequences from it. That had to have a major impact on attitudes of the potential aggressor states toward the US. It encouraged the Germans and Italians, as well as the Japanese to think that the US had gone soft. It probably played a role in Hitler's thinking as he approached the decisions that led to World War II. 

What might have happened: The crew of the Panay attempted to fight back in our time-line. They didn't have much to work with because the first Japanese bombing run took out their main armament (along with their radio). On the other hand, small arms fire does occasionally take down low-flying planes. When it does, the shot that does the damage is called a “golden BB”. Let's say the crew of the Panay do shoot down one of the Japanese planes. It spirals in and crashes on camera. 

Nothing much else changes until the Roosevelt administration tries to talk the camera crew into withholding the most damning footage. That doesn't work in this time-line. First, everyone has heard that a Japanese plane was shot down, and they want to see that. If that footage isn't shown, its absence will be obvious. Also, that footage makes the reels incredibly valuable. They get shown in their entirety. 

The Panay incident now resonates in the American psyche. It can be seen as a modern day Alamo, where outnumbered Americans fight back desperately and effectively against an overwhelming enemy. It doesn't destroy isolationism, but it changes a lot of minds in the United States. Those changed minds gradually lead to a less isolationist House and Senate, especially as the stories of Japanese atrocities in Nanking seep out and in the anti-Japanese atmosphere following the Panay incident, are believed. 

The changed Panay incident doesn't lead to a declaration of war on Japan, but it does lead to a major American loan to the Nationalist Chinese, increased US military spending, and a lot of US military aid to the Nationalists. That, in turn, helps the Nationalists stop the Japanese outside the key Chinese industrial town of Wuhan.

The incident now has a very different symbolic impact on the rest of the world. The US is seen to have fought back effectively, and cannot as easily be categorized as one of the 'decadent western democracies'. Where do we go from here? Does that “Golden BB” derail World War II or make it unrecognizable, or do the ripples gradually die out? Would you like for me to explore the implications of this in more depth next issue?