What is the ruling on congregational prayer in the desert without the adhan or iqamah?

The Shaykh : A group of young men went out to the desert, and when the time for the 'Asr prayer became obligatory, one of them led the rest in prayer without the adhan or iqamah, even though he had forgotten. What is the ruling, considering that he did not remember that he had forgotten the adhan and iqamah until after the takbir?
The ruling is that the prayer is valid, even if it was done intentionally, because the adhan and iqamah are obligatory for the prayer, not obligatory within it. There is a difference between what is obligatory for the prayer and what is obligatory within it. Do you understand, my brother?