What going on in this picture?

[Tony Smith]

Two points.

If it is an AIF unit, then the blokes will be AEME, not REME.

Secondly, Frank Hurley was famous/notorious for composing and/or recreating his pictures as recreations or even compositions, rather than actual "during the battle" scenes. This photo could well be a re-enactment. He felt it was far more important to convey the many elements of what he was depicting, rather than simply record an actual battle. He was essentially an artist using photography as a medium, rather than a chronicler recording actual events. That philosophy brought him into conflict with many in the Military, historians and journalists, but most of his pictures are so well composed technically, that many have become iconic images of war. Some of the AIF troops felt disdain for him as he treated them like actors when recreating scenes rather than follow them into battle. His personal courage cannot be doubted though, as his photgraphic career included many life-threatening highlights including being stranded on pack-ice with Shackelton's 1914 Antarctic expedition. A brief highlight of his career is HERE

Have a read of how it was normally done: HERE