Trump to invoke Alien Enemies Act in coming days (article linked)

https://www.cnn.com/2025/03/13/politics/alien-enemies-act-deportation-consideration/index.html

Just some quick quotes that stuck out to me:

“The announcement, which could come as soon as Friday, has been a moving target as officials finalize the details.”

“The law is designed to be invoked if the US is at war with another country, or a foreign nation has invaded the US or threatened to do so. Legal experts say it would be difficult for Trump to use the act when the US isn’t being attacked by a foreign government, even if the administration does cite threats from gangs or cartels.”

“The Alien Enemies Act has been invoked three times in US history – all during war – according to the Brennan Center.”

My question is; Who are we declaring war on? (Not that I think it’s going to really stop him from just saying “the cartels.”)

EDIT: I do want to follow up with this post and add that he is visiting the DOJ today (3/14). Some are speculating he will sign/allude to signing the act there. Will try to update