Post Mortem of a Mistake
Remember that David's armies had defeated Nahash of Ammon, who insulted David's messengers, and his alliance which included the Syrians. Now, the following year, Joab leads a campaign against them that reaches into the heart of their kingdom, besieging their very capital city. (Remember the Ammonites descended from the son/grandson of Lot. When Israel took the Promised Land God told them to respect Ammon's borders. The two nations had an uneasy brotherhood that was on and off again...mostly off...throughout their history. Now they had openly insulted David and David's army retaliated.)
Joab broke through the strength of their capital city. Just before the military victory was complete, Joab sent to David saying almost sarcastically, ""Come over here and at least take credit for this, if that's not too much to ask. Otherwise they'll name the city after me." Joab was a lot of things that were despicable, but he did seem to have a real investment in David's interests.
David came with the rest of the army, and they finished off the capital city, taking their kings' crown that weighed 131 pounds! (And more amazingly, setting it on his head...I wonder if there is something I am missing here? Perhaps the weight was "weight worth in gold?") He also claimed the spoil of the city, and made the Ammonites slaves.
So why, again, was David not fighting with his army?
Uriah proved himself a far better man when he refused to be comfortable while his comrades suffered in the field. He would not even go home at night...so dedicated was he to the cause. David, it seems, was happy to stay at home in comfort, even carefree enough to think of indulging his lusts. He had been sleeping all day when he saw Bathsheba.
Perhaps he was indulging in self-pity because of the recent snafu with Nahash, to whom he tried to show kindness. Now embittered about the situation and the messy war that had ensued, he wanted no more to do with it. Maybe also he felt he just needed a break from fighting every year. This would be his season to take a break and recharge. His self-indulgence left him weakened to temptation. Caught "without his armor," he was easy prey to his own lusts.
Far from despising David, I recognize too much of my own heart in him. I often become desensitized to my responsibilities in favor of self-gratification, discouragement, and self-pity!