The B3A was the first modern all-metal carrier-based dive bomber designed to replace the preceding carrier air fleets of older bombers in 1939.
The development of the B3A Dive bomber was not a smooth ride: initially in 1936, she was plagued with engine issues which required her to reduce her payload capacity, from her usual 1000lbs of payload to 500lbs and even that wasn't enough. Due to her rather mediocre engines, she could only top at a maximum speed of 320km/h. It was only in 1938 when a new engine developed by Satsuma Motors actually presented the development teams a new twin-row super-charged 18-cylinder radial engine, which is a whole level larger and more powerful than the previous engine developed by the Mann Co. Motors which is a single-row 10-cylinder engines.
The new engines, however, meant that the engine cowling had to be made longer to accommodate the new engine. And in the same year, the first prototype made its first maiden flight with both full fuel capacity and full bomb payload, all passed with flying colours. No pun intended.
Due to her nature of being a bomber, she was, by default, fitted with twin 12.7mm Type-36 Machine guns, which was developed back in 1936 for this dive bomber, for her rear gunner, and a pair of 7.62mm machine guns on the nose, having synchronization firing mechanism.
Her first taste of action was during the Bosgovinan Civil War in 1940, where she was sold to the Imperialist side of the country to fight against the Socialist side of the county. In this version, her carrier capabilities are all discarded to make her as an export version. During this war, only 3 squadrons worth of B3A Dive Bombers are in service for the Imperial Bosgovinan union. It was in this civil war where the Satsuman Imperium had realised one flaw that was easily remedied in the follow-up models: diving flaps. During this war, at least 6 B3As were lost in battle, mostly due to them not able to pull up from the dive. According to some witness accounts and some visual evidence, their flaps broke off from the wings while going too fast on a steep dive. This led the industries to produce the most widely produced B3A-C Variant, with the famous cheese-grate flaps to prevent them from breaking out of the wings while slowing the dive bomber down just enough to help pilots safely pull-up. Believe it or not, it was an inspiration from a bored designer who noticed some holes on a piece of fabric to prevent it from flying out while still maintaining, to some degree, it's position.
The Bosgovinan Civil War was just the field test. and it's only true test in the wars was during the Raid of the Golden Bay, in 1942, against their major naval rival since the dawn of Empires, the Sabrian Empire.
The Golden Bay was Satsuman Imperium's strategically important naval base in the Endless Ocean. In there, seven squadrons of carrier-based B3As were there on reserves, waiting to be deployed on a new carrier taskforce. Though that was never to be in this case.
In the Raid of the Golden Bay, Satsuman Imperium was caught off-guard for the first time in its history. Many battleships, mostly from the 1910s, are hit and damaged, or worse of all, sunk with the worse damage. But that's just the beginning.
In the airfield close to the harbour, many B3As are either damaged or just straight-up destroyed, save for a few bombers spared from the onslaught. Because the fighters in reserves are all destroyed or incapacitated, these remaining 7 B3As are their only last hope to clear the sky, filled with Sabrian DB-3 Crusader Dive-bombers, F-7 Marauder Fighters, and TB-9 Comet Torpedo Bombers which were leagues faster and more agile than what Satsuman Imperium had at that time.
Their next action was during the retaliatory raid against Sabrian naval holdings on the Fort Myers in 1943 where they fought alongside with a squadron of new but prototype torpedo bombers, the J-84C "Pelicans", with one objective; hit hard where it hurts the most. While not as painful as they would have wanted, it certainly gave the Sabrian Empire a taste of their own medicine
However, their true tests in hell was the Battle of the Moonstone Island, an island chain which is gob-smacked in the middle of the Endless Ocean between the two Empires. Prior to the battle, the B3As had to fly for hours until they finally spotted the massive combined fleet of Sabrian Carrier Armada, comprised of 6 fleet carriers and four light carriers, against Satsuman Soen No Kantai Carrier fleets of four fleet carriers, two of which are conversions of their preceding battlecruisers, and two light carriers.
While they had already proven their battle capabilities, they were slowly replaced by fleets of more modern dive bombers. Keyword is slowly mainly because newer dive bombers that was supposed to be better than B3As had so much issues in their production that the Navy ended up using the B3As up until the very end.
Their last action while under Satsuman Naval service was in 1947, during the Sabrian last-ditch naval operation code-named Operation Sirens of Ulysses. There, nearly 60 remaining B3A, or more specifically the B3A-F Variant, had fought against the Sabrian Superbattleship.
While it went out of service for Satsuma, other nations were interested in using them to build up their national air forces. The most prominent user of this dive bomber outside of Satsuma was the Kingdom of Estor, who was desperate for anything that they can use to protect themselves against their neighbouring countries. And surprisingly for a dive-bomber made in the late 1930s, they continued on staying in service until the last squadron had replaced them in 1987, where they were replaced by A15D "Eagle" and A14D "Tengu" fighter-bombers.