All I Know Is That I Must Kill is Image of a Russian servicemember wearing a Maska SCh1 helmet. It is most common used either sincerely or ironically about gamers and their attitudes to games, particularly first-person shooters. It is used in a similar capacity to the Stealth is optional for this mission meme and is related to the Lord Tachanka meme as they both a similar look by wearing the Maska SCh1 helmet.
The predecessor of the meme and origin of the phrase started on /k/. The variation was first uploaded to Imgur on December 21st, 2014 where it has gotten 2,009 views.
On October 20th, 2018, the image was uploaded to Reddit by user u/_AllMight to r/memes, where it has gained over 4,000 points.