Avoid Windfalls: If a deception target obtains deceptive information too easily ("too good to be true"), the target is unlikely to act on it and the deception will fail. This requires deception planners to take care in placing deceptive information so that it will appear to have been acquired in a seemingly natural manner. The deception target is then able to assemble details from multiple sources into a coherent, believable, but untrue story. The best deception plans co-opt the enemy's skepticism through requiring enemy participation, either by expending time and resources in obtaining the deceptive information, or by devoting significant effort to interpreting it. In an example of valid information being dismissed as a windfall, early in World War II a plane carrying German officers to Cologne became lost in bad weather and landed in Belgium. Before being arrested by Belgian authorities, the Germans attempted to burn the papers they were carrying, which included copies of the actual invasion plans for Belgium and the Netherlands. Belgian authorities discounted this true information as false because of the ease with which they obtained it.