“… Fatalism is thought to be meshed in Islam. “Inshallah” - if God wills it - can breed a sense of resignation, a “why bother?” attitude. That’s the opposite of taking charge and getting things done. It’s also used by non-religious Arabs and it really predates Islam. I was in Iraq for a bit during the second Gulf War and I talked to a young American soldier who was training Iraqis to take over. He said that time and time again their soldiers would literally hold their rifles above their head to shoot. Their belief was that God would guide those bullets, so it really didn't matter if they aimed their guns at all. That’s not great soldiering.”
Source: “Why Can’t Arab Armies Beat the West?” (9:55)
Link:
https://www.youtube.com/watch?v=robmO5AKJ8
“Deus vult” — “God wills it” — was the rallying cry of the First Crusade. Unlike “IF God wills it,” the phrase asserts divine approval, not possibility. That’s a qualitative difference.