What's an Infantryman?

I'm often asked here and elsewhere what exactly an Infantryman is and/or does.

Robert Heinlein described them as the ultimate purpose and arm of the entire military. No other unit exists but to support the infantry directly or obliquely.

I'm an indirect fire Infantryman.. Which means I lead a heavy mortar section (2 120mm cannon crews). In conventional combat our role would be to serve as the commander's first indirect fire asset. We're his hip pocket artillery. Fast, accurate, and extremely destructive, our wide range of ammunition allows us to support front line infantry in almost every situation.

But what's an infantryman? Here's some links I find especially appropriate:

He's an Infantryman

The Infantryman's Creed

Wiki's infantryman page

The Go Infantry Forum

This should give you the flavor of who we are, and maybe what makes us tick (we're all mad, if you really must know).