In total, the campaign sent out 4 unique mailers to different influencers worldwide, from which an additional 4 campaign beats “unlocked” via cyphers on the decoder site. Through 22 assets that included time-worn envelopes, handwritten letters, art rubbings, vintage photographs, zombie medical sketches, and more, we were able to tease, misdirect, and set the stage for Call of Duty’s most ambitious Zombie experience to date.

By encouraging each influencer to open, experience, and solve each letter for their audience, we turned each batch of content into an experience and allowed the community to interact with their influencers as they debated details, guessed at plot points, and solved for the cypher code together.

Each letter we sent to influencers held a secret cypher code that unlocked the next stage of the campaign. To access this embedded content, fans had to solve for clues that confirmed they had to ‘heat’ the letters to reveal the cypher. In the early 20th century, German forces encrypted secrets to one another using lemon juice — we reemployed the same technique used by these spies, painting cypher codes in lemon juice, which influencers unlocked live on their broadcasts.

In our narrative, a brother and sister communicate via letters…until Nazi leadership gets suspicious. At this point, the brother pens letters in secret, writing on whatever paper he can steal. We sourced actual vintage German books printed in the 1940s that he’d write on, including Goethe’s “Faust” and a German reference book on the Egyptian pyramids, which misdirected online conspiracy theorists.

Armed with the lemon code cyphers, fans ‘unlocked’ accompanying content streams on a special decoder site. There, they could read the sister’s diary entry responses to her brother’s increasingly frantic letters, and her plans to help him — setting the stage for the entire Zombies mode to come. These journal page scans tied to the physical letters by showing the influencers’ letters tucked into its pages.

The goal: each package had to feel like it traveled through time to our influencers. To do this, the Armed Mind team ensured every asset in the campaign was painstakingly authentic to the 1940s. Our paper stock was bona fide 70+ year old parchment, our ink was the same type of oak gall ink a German soldier in 1941 would have used, and each page was hand-written with an authentic fountain pen. From there, each page was aged, rubbed in dirt, and distressed until it felt plucked from another era.