After Krakabloa became a country of it's own, it quickly became very clear there was a severe shortage of oil. Krakabloa was desperate for fuel to keep it's industry up and running. Thus the desission was made to invade Maywar, and capture it's massive oil fields.

While invading Maywar, Krakabloa's Millitary realised that the enemy had far greater air power, with performance figures that crushed those of the 01Z... It was time for an upgrade: the 01S.

Featuring a monowing design, a longer fuselage and a blistering topspeed of 238mph (which was 60mph faster than the 01Z). It is also way lighter, making it far more maneuverable. But all these benefits did come at a cost, as the 01S can carry alot less fuel.

The 01S is nowadays often seen as "the reason Krakabloa won the 1931 May war".