John Gill Commentary 2 Samuel 11:15

"And he wrote in the letter, saying, Set ye Uriah in the forefront of the hottest battle, and retire ye from him, that he may be smitten, and die." — 2 Samuel 11:15 (ASV)

And he wrote in the letter, saying Giving the following orders to Joab:

set you Uriah is the forefront of the hottest battle : over against that part of the city where the enemy was strongest, and the battle the fiercest, and the stones and arrows were cast the thickest:

and retire you from him ; leave him to himself to combat the enemy alone; who seeing him deserted, would sally out upon him, and the few that might be with him, and slay him:

that he may be smitten, and die ; thus he sought to add murder to adultery, and that in the basest manner, and which he accomplished; and this is often the case, that murder follows adultery, either by way of revenge for it, or in order to cover it, as here.