3U 2T 1A 3U 5T 1U 4G 4U 5T 2G 4A 5T 4U 3G 3G 5T

2G 2T 2T 5T 4U 3G 5T 4U 3T 1A 4U 1S 2T 5G

3A 3G 3U 4U 2A 3G 3A 1S 3T 5A 5T 4U 3G 5T

1G 3G 3A 3A 1A 3U 1U 5G

Then he said, “This is what we call a ‘calendar code.’ The key is the first line. The eighth month of the year is August. Our Committees of Safety have been using these codes for more than a year—too long in my estimation. Here’s how this one works.” With Col. Arnold looking over his shoulder, Capt. Morgan took a blank sheet of paper and explained:

“To create an ‘August code,’ write the letters of the month across the top line and beneath each letter of the month, place sequential letters of the alphabet like this, five rows and six columns. A number and a letter represent each letter of the coded message. So, the first letter of the message, 1T is F. The second letter, 3A is M. The third entry, 5T is a space. 3U is P, 4A is S, and so on . . .

“Now, see how quickly young Nathanael can decrypt this message.” I began to write . . .

FM PS TO GW [from Philip Schuyler to George Washington?]

SCHUYLER APPROVES

PLAN BUT IS TOO

ILL TO TRAVEL.

MONTGOMERY TO

COMMAND.

As I was decoding the message, Col. Arnold asked, “Captain, why do you say the Committees of Safety have been using this type of code too long?”

“Well, sir, first, the British are better than we are at code-making and breaking. You may recall it was the intercept of a coded French message that alerted General Forbes about the deplorable conditions at Fort Duquesne in November of ’58. The French code was broken by the British nearly a year earlier, but the French were still using it. That’s why Forbes pressed on, despite Col. Washington’s advice, and the French garrison burned Fort Duquesne and fled.

“Second, our ‘calendar codes’ are simple to use. They can be encrypted and decrypted quickly and neither the sender nor recipient needs a codebook. Unfortunately, six of the ‘month codes’ have repeat letters like August’s two U’s. December is impossible with three E letters. ‘daily codes’ are somewhat better because they change every twenty-four hours but ‘Wednesday’ with two letters ‘D’ and ‘E’ is impossible. Given how many of these ­‘calendar coded’ messages have been dispatched by our various Committees over the last two years, I have to believe the British can break them as fast as my young Adjutant.”