For Keith Willshaw...

000 is less than 3800

Obviously 10000,sorry for typo.

August comes after April
Right but still question was about April.

Thats what typically happens when priorities change

No,as soon as Japanese fleet assembled in early Nov.,OP-20-GY -1 was alerted
and devoted almost all of its resorces to JN25B messages on 7/24 basis.

Extra money, people and equipment made it happen, just as the
US armed forces increased in size rather quickly, this tends
to happen during a major shooting war.

Problem is that the US knew that it was going to happen almost one full year in
advance.

Safford is not a good source, but since only 3,800 had been cracked !

Safford is pretty good source if you add up monthly totals you will find
another number

Nope.

True sir US,(and Probably Brits) were able to read almost 90% of Jn25B
dispatches prior to Dec.7