What made the Doolittle Raid possible?

The main reason why the Doolittle Raid was so unexpected by the Japanese was because with the american aircraft of the time and lack of an American (or allied power) airfield close enough, leading a heavy bombing mission to bomb Tokyo was practically impossible. This leads to the question: how did we pull it off? The simple answer is good engineering, great pilots, and a whole lot of luck. Let's start with the planes. The first challenge was finding an aircraft that could fit on an aircraft carrier and still land a decisive blow to the Japanese mainland. The planes that operated from carriers at that time (before steam and magnetic catapults) were limited to fighters, lightly armed reconnaissance planes, and medium torpedo bombers. None of these were capable of carrying enough ordinance to make much of a difference to the Japanese supply chains. This meant that they had to find a way to make heavier bombers fit and operate from carriers. Six candidate planes were chosen for testing. Planes like the B-17 and B-23 were deemed unsuitable due to their large size. Others like the B-26 Were eliminated because of their handling characteristics. Eventually, the AAF (Army Air Force) settled on the B-25 Mitchell. The B-25 was small enough to fit several on the deck of the USS Hornet yet large enough to drop several tons of bombs on the Japanese capital. However, the B-25 was by no stretch of the imagination well suited for carrier operations. This is where the engineering came into play. AAF mechanics stripped out every ounce of weight that they could, stripping out kevlar fabric (Bulletproofing material that is common in body armor. At this time it was used to line the insides of bombers to protect the crew and payload from small arms and light anti aircraft fire), most of the .50 caliber machine guns that the B-25 used for protection, Bombsights (The crews used much lighter makeshift bombsights on the mission in an effort to save weight, and most of the regular flight equipment (Fire extinguishers, most of the avionics, and all but one radio) leaving the bare essentials for the mission. All of this lightened the bombers by about 1500 lbs each. The lighter weight made the bombers takeoff distance significantly shorter than a regular B-25. Although the aircraft were now capable from operating on the short aircraft carrier flight decks, skilled crews were needed to make the takeoff and complete the mission. The 17th bomb group of the AAF was selected to provide crews for the mission. Sixteen of the best bomb crews in the AAF were selected. These crews spent the next seven months training in Norfolk, practicing extremely short takeoffs, evasive maneuvers, and night navigation. In the end however, all of this training and engineering would not have made much of a difference without the luck that task force 18 had as they transported Doolittle's planes to Japanese waters. The carrier group was spotted around 750 nautical miles from japan by the japanese patrol boat Nittō Maru which was quickly sunk by The USS Nashville before a clear warning could be sent to mainland Japan. The fleet dodged Japanese air patrols for the next 100 nautical miles before they could launch their attack. If any of these factors had failed, then Doolittle's raid would have almost certainly failed.