In this portion of Samuel, we see David commit his first major sin since he came onto the scene. We've slowly been watching David get a little full of himself over the last several chapters, but he has always managed to save face in God's eyes...until now...
In Chapter 10, we learn that the current Ammonite king has died and now his son, Hanun becomes king. David sends some of his servants to pass along condolences to the new king, trying to show a little compassion and show that they could remain pseudo-allies. However the servants of Hanun recommended that he not trust this gesture from David and implied that David was sending spies. So he ordered his servants to shave half the beards off of David's servants and cut-off half of their clothes (picture, down the middle), "even to their buttocks." This seems a bit prank-ish :)
So then the Ammonites gathered together people to take down David, failed, and David said, "You're on your own now, fellas...I was trying to be nice, but you asked for it!" Then the rest of the neighboring nations saw how powerful David was and decided not to mess with him and told the people of Ammon that they were on their own, leaving Ammon, well--on their own.
Now after they took over an Ammonite territory, David was lurking around one night and what to his wandering eye should appear but a little hottie named Bathsheba. So he called for her, "lay" with her, and sent her back home. Then Bathsheba sent a message to David that she was with child. Now, mind you, Bathsheba was the wife of Uriah the Hittite (one of David's men). So David sent for Uriah and acted like he was looking for a report about how the war was going, and then sent him back home. But Uriah said, "No, I'm going to stay here. How can I go home to my wife when all my buddies are out here fighting for Israel?" So David "let" him stay the night, conveniently got him drunk, and sent a letter to Joab (one of his captains) asking him to put Uriah in the forefront of the "hottest battle." Basically, David knew he was sending Uriah out to die. And Uriah died. So David called for Bathsheba, Uriah's mourning wife, and took her as his wife and she had their child. But the thing that David had done displeased the Lord.
In Chapter 12, we hear again of Nathan one of the prophets in David's kingdom. God sends Nathan to David with a parable about a rich man with lots of sheep and a poor man with one sheep that is like a pet. There was a traveler who visited the rich man and the rich man took the poor man's sheep and fed it to the traveler. When David heard the parable, he said, "Surely the rich man will die because he did such a terrible thing and had no pity," to which Nathan replies, "Dude, you're the rich man...God's ticked because you took what you thought you deserved (even though God gave you more than enough) and broke a commandment and had no remorse." David says, "Yeah, I sinned." And Nathan says, "God will let you live and he does forgive you...but you are going to pay for your sins." So when Bathsheba has their child, the child is born sick. Seven days later, the child dies. The days that the child lived, David fasted, wept, and prayed, asking God to spare his son (his repenting). After the child dies (his penance), David goes to comfort Bathsheba and gets her pregnant again, but this time God lets the baby live...and this baby was Solomon.
At the end of Chapter 12, David finishes conquering Ammon.
Interesting stuff! We're learning a lot about David that we never knew!