139 - Allied Intelligence cracks Japanese codes! - WW2 - April 25, 1942

by Panzer
You sent them how many planes?
Wow, that's great!
Now they can really fight back, right?
What?
No, they're all destroyed.
But didn't they get there just two days ago?
Oh.
That's not good.
Uhuh. Okay.
April 25, 1942
If you have an intelligence unit and you've sort of cracked some of the enemy's main code
and have a rough idea of how it works, what would be the best thing for you to have to
expand on that?
Tons and tons of the enemy's radio traffic.
I'm Indy Neidell; this is World War Two.
Last week, the Japanese advance through Burma continued, and Burma Corps Commander William
Slim ordered the destruction of local oil installations to prevent them falling into
Japanese hands.
There was a bit of a black eye for Japan, however, as Tokyo was bombed by American B-25
bombers in the Doolittle Raid.
That had a bunch of quick repercussions, even though the bombing itself did very little damage.
For one thing, it caused the Imperial Japanese Navy to send out pretty much every warship
of the Combined Fleet at the beginning of this week to try and catch Admiral Bull Halsey's
task force- the ships that had launched the assault planes.
It easily gets away, but this action has some unintended consequences.
Here's a little backstory- Japan had a plan to mount an amphibious assault that was to
take Port Moresby last month, called Operation MO.
This was to have aerial support from only land based bombers from Rabaul and seaplanes
from new bases, but an American air raid back on March 10th alerted Admiral Shigeyoshi Inouye
that there was an enemy carrier force in the area, so he wanted to postpone MO until he
could bring in Japanese carrier support to ensure aerial superiority.
Combined Fleet Commander Isoroku Yamamoto allowed him to postpone it till May.
During the wait for that carrier support, Inouye has taken the time to build a defense
perimeter from the Solomon Islands to the Philippines.
Well, now on the 23rd, Inouye issues South Seas Force Order #13 to resume operations
against Port Moresby.
He will have the fleet carriers Shokaku and Zuikaku and the light carrier Shoho for the
first two weeks of May with his Fourth Fleet.
A lot of the communications for this operation and other plans for phase two of the Japanese