A company has multiple AWS accounts.

Create an organization in AWS Organizations. Set up AWS Control Tower, and turn on the strongly recommended guardrails. Join all accounts to the organization. Categorize the AWS accounts into OUs.

Use the AWS CLI to list all the unencrypted volumes in all the AWS accounts. Run a script to encrypt all the unencrypted volumes in place.

Create a snapshot of each unencrypted volume. Create a new encrypted volume from the unencrypted snapshot. Detach the existing volume, and replace it with the encrypted volume.

Create an organization in AWS Organizations. Set up AWS Control Tower, and turn on the mandatory guardrails. Join all accounts to the organization. Categorize the AWS accounts into OUs.

Turn on AWS CloudTrail. Configure an Amazon EventBridge (Amazon CloudWatch Events) rule to detect and automatically encrypt unencrypted volumes.