Answer:
In wars, secret codes are used to hide information from the enemy.
Step-by-step explanation:
Honestly, a hook sentence just can be a random fact, question, or whatever that is related to your claim/thesis.
For example, a question could be, "Have you ever created a secret code with someone?"
A fact could be, "About 420 people were Navajo code talkers in World War II."
Just put something interesting and it works!