I believe that many of these movies of this type are epics and that the central conflict is between two entities that are much bigger than the characters involved in the story. The central conflict here would be between the United States and Germany, with the United States being the protagonist, since they are on the offensive. The characters in the story are just little people who are caught up in a conflict which is far greater in size and importance than themselves. They are acting because they are under orders. The same was true of the movie Gallipoli. Even in Tolstoy's great novel War and Peace the central conflict was between France and Russia. In Gone with the Wind the central conflict is between the North and the South, and in that novel the North is the protagonist because they are invading Georgia. In Ambrose Bierce's short story "An Occurrence at Owl Creek Bridge," the central conflict is also between the North and the South in the Civil War, and in that story the North is the protagonist because the Union Army is invading the South.
So the central conflict in Findinig Forrester would have to be described as man versus man, as it would be in any war movie or war novel. I believe it makes it easier to understand war stories if you think of them as epics, like Homer's Iliad, and think of the central conflict as one between great powers. The characters in the story typically have little control over their actions or their fates. They are just doing what they have to do because they are caught up in a great conflict.