Eliminating a Branch of the Military

We often get questions about which is the "best" military service, or why can't one service replace another service.

Each of the services have their own distinct mission and capabilities. However, it would be possible (although possibly not wise) to eliminate one (or more) of the services and have a different service pick up their mission.

So, this week's question is which service is expendable?

If we absolutely had to eliminate one branch of the military, which branch should be eliminated?