I can see there are many challenges here. This may seem simplistic, but with regard to this difference in the OSIs of army veterans as opposed to those for navy and air force veterans, might it have to do with the fact that when you're on the ground in a deployment, the realities of the violence and the impacts of that hostility are greater because you're there on the ground, as opposed to being on a ship or in the air? The others are still part of the deployment but not on the ground.
On March 20th, 2017. See this statement in context.