I've never served so this is the first time I've heard of the "Army Strong" raised fist tradition. But it's interesting that only black fists are considered political gestures.
https://news.vice.com/article/black-female-cadets-under-investigation-for-raised-fist-picture
https://news.vice.com/article/black-female-cadets-under-investigation-for-raised-fist-picture
US military officials are investigating an image of 16 black female cadets in uniform with their fists raised, which some say is a political act associated with African-Americans' quest for fair treatment under the law in the United States.
The photo came under scrutiny when concerns were raised that the pose violates West Point's honor code, which mirrors the Defense Department's federal Hatch Act, in that it prohibits members of the military to participate in political activities while in uniform.
The raised-fist image is now closely associated with the #BlackLivesMatter movement, which swept the country in the wake of several high-profile police killings of unarmed black men. The image picked up some traffic online, and drew criticism that the woman were expressing support for the movement, which is critical of law enforcement. For example, one twitter user under the slogan "BlueLivesMatter" a counter slogan supporting police was incensed. "Expel them and force them to repay their tuition" she wrote.
Fulton also points out that there's another tradition at West Point, wherein cadets raise their fists whenever the "Army Strong" theme from the recruitment commercials is played (as demonstrated in the video below). "It is unfortunate that a black first has a different connotation to a white fist," Fulton said. "It's not what these young women intended."