A tweet by Elon Musk on the fall of Constantinople (Istanbul) has baffled social media users worldwide and has caused hundreds of predominantly negative reactions in Turkey, according to Greek Reporter.

The Tesla founder and billionaire tweeted a meme of a Byzantine soldier who is in bed thinking to himself whether he “locked the gate” and under the image: 1453 Constantinople.

The Fall of Constantinople was the capture of the capital of the Byzantine Empire by the Ottoman Turks. The city fell to the forces led by the Ottoman Turkish Sultan, Mohammed (Mehmet) II on May 29, 1453.

Musk’s cryptic tweet has puzzled many, with Turkish users asking themselves whether it was a positive or negative tweet. Or why did Musk refer to the date the city fell? Or why didn’t he call it Istanbul?