This lesson correlates to the National History Standards.
 Era 7-The Emergence of Modern America (1890 - 1930) o Standard 2B-Demonstrate understanding of the causes of World War I and why the United States intervened.
This lesson also correlates to the National Standards for Civics and Government.
 Standard IV.A.2-Explain how nation-states interact with each other.
Share this exercise with your history and mathematics colleagues.
Teaching Suggestions
1.
Decoding a Message
: In this exercise, students decode a fictitious message using a simple substitution code. As homework, ask students to write a message using the code, and then exchange the messages for decoding.
2.
The Zimmermann telegram provides an opportunity to review geography with your students. Ask them to locate England, Germany, Mexico, and Japan on a world map or globe. Direct students to indicate on the map or globe the territory offered by the
Germans to the Mexicans in the telegram. Ask them to calculate how much the territory offered to Mexico would increase the size of that country. What geographical advantages would the Germans gain by Mexican entry into the war? What was the role of Japan?
3.
Discussion questions: a.
What other documents have changed the course of American history? For example, consider the effects of the Emancipation Proclamation, the Monroe
Doctrine, and the DeLome Letter.

b.
What events in 1916 and 1917 contributed to the impact the Zimmermann telegram would have on the American public? c.
Would the United States have remained neutral if the Zimmermann telegram had not been revealed?

In substitution codes, the letters of the plaintext (message to be put into secret form) are replaced by other letters, numbers, or symbols. In this code system, each letter of the alphabet and each of the numbers from 1 to 9 appears in the matrix of the grid. Each letter in the grid is replaced by two letters in the coded message. The first letter in the message is from the vertical axis of the grid, and the second letter is from its horizontal axis. For example, if "DG" were the first two letters to decipher in a cryptogram, you would find the letter "D" on the vertical axis and the letter "G" on the horizontal axis. Trace them across the grid to their intersection at the letter "A" in the plaintext.
To decode the fictitious message in the cryptogram, begin by grouping each set of two letters starting with the first two letters (FG) and continuing through the message. The code letters are arbitrarily arranged in groups of five letters. Some letter pairs will carry over from one line to the next. As you locate each letter in the grid, you should write that letter above the pair of code letters to which it corresponds. There are no punctuation marks in the telegram, so your teacher may need to help you in clarifying the message.
Cryptogram
FGAFA AAVXA DGAVX VADAD DVDD
D
VGA
VXVDX DVDDF AFDXG XGDD
G
AVFDV X
VAAFX GDAD
X
VDDX
D
AVXXV
AAAVD AVXDA VVGD
D
XAVDG DXGXV XVDVF VVAFD XAVAF
VXDXV DFDAF XAVVV FAVAF VVVVV ADGXV AXAFD GGXFX AFAVV

ADGD
F
VFAXV DVXXF DAVXG DVAAF XGDA
D
XVDVF AVAFV FDGA
V
AFVXV DAXAF DGXD
A
FAFVA AADGV VVVXV VDDF
V
VGDV
D
AVVX
D
FVDVX DADXA F
XVDDF FDDX
AAAFA VDFVV VXVDA VFGFG XFDGV VGDD
A
DFFXV
Grid
A
D
F
G
V
X
A
U
D
V
F
W
G
X
V
Y
X
B 2 E 5 R L
I 9 N A 1 C
3 D 4 F 6 G
7 H 8 J 0 K
M O P Q S T
Z
Teachers: Should your Web browser not display the above material correctly, you may access a JPEG image of the Crytogram and Grid.