United States Marine Corps USMC, SIGINT/EW Marines Marine Cryptologic Support Battalion 1st Radio Battalion 2nd Radio Battalion 3rd Radio Battalion
Roll Call

The Code Breakers
Making Knowledge from Numbers

Sample Vietnamese Code Matrix
  0 1 2 3 4 5 6 7 8 9
0     b     a     1  
1       g   ế     2 f
2   n     au i   v   0
3     q     ô       6
4 Kh     ou   u   d   5
5     nh     y t   4  
6   c     r       k h
7 w     ph   oi   m 7  
8 x s p   v   l 8   z
9               9 ng 10
Tôi Không Biết (I don't Know*) = 56, 35, 25, 40, 35, 98, 02, 25, 15, 56 where radio operators would say numbers in Vietnamese  56 = Nam Sau, 25 = Hai Nam, etc.

Of course different tones on the vowels would be added as well, but just a couple are shown in this matrix (25 and 35.)  We would look over a message, see which code matrix best applied, then translated message into Vietnamese, then English.

If the coded message didn't match an existing matrix, then the cryptographers would do their thing, sit with a linguist and attempt to begin filling in the blanks.  The more messages received by a particular unit, the more blanks were filled in.  This assumed that the numbers we received were 100% accurate and not garbled transmissions.

Now, follow this scenario - Memorize the matrices you expect to see during the watch.  When radio traffic is received:
1. One person listens to the series of numbers that are being transmitted by the VC in spoken Vietnamese; write them down in pairs.  After they have a few number pairs written, the
2. second person analyzes the pattern to determine which matrix map to recall from their memory, writes the Vietnamese letter or diphthong represented by the pair of numbers, and
3. second person also writes the English translation above the Vietnamese.

Meanwhile, the first person continues to listen and write more number pairs
That process would look something like this:
 I                   d   o       n   o   t        k   n   o   w
2 t ô i Kh ô ng b i ế t
1 56 35 25 40 35 98 2 25 15 56
* Little known story reported by Joe Stearne:  When in Vietnam in 1962 we were attached to the Army Security Agency unit 3rd RRU and they had their shield and it said "Cum Bi'et" [Ed; A different dialect than above] which means " I don't know". Well it didn't take long before our little Marine sub unit took exception to that and commissioned me to come up with an alternative badge design to counter the Army's. The badge on the Home page is my work- "Bi'et Chāć", "Know for sure".