Which military branch deploys first?

Feeling pretty stressed about this, but it's something I need to know: should a war occur, which branch of the military usually gets sent to the front lines first? Is there a standard protocol for this?

Typically, the role of first response or quick reaction in times of a military conflict often falls to the special operations units of all branches, which include the units like the Army Rangers, Navy SEALS, and Marine Corps' Force Reconnaissance. These are highly-trained units tasked with a variety of missions which could include direct action, unconventional warfare, reconnaissance, and many more.

Standard protocol, however, does not mandate a specific branch to always be first on the 'front lines'. The deployment of specific military branches depends largely on the nature of the conflict, the theater of operations, strategic goals, and mission requirements.

For instance, if the conflict involves significant maritime operations, the Navy or Marine Corps may be among the first to respond. By the same token, if the operations in question are more ground-oriented, the Army might be the first to be deployed.

Importantly, the term 'front lines' has evolved significantly with modern warfare. Rather than a clear delineation as in previous eras, today's battlefields can be non-linear and highly fluid with the advent of technologies like drones, missile systems, and cyber warfare. It's worth noting that, in today's interconnected military structure, all branches play crucial roles irrespective of who is technically 'first' on the scene.