And it came to pass, that after the year was expired, at the time that kings go out to battle, Joab led forth the power of the army, and wasted the country of the children of Ammon, and came and besieged Rabbah. But David tarried at Jerusalem. And Joab smote Rabbah, and destroyed it.

And it came to pass, at the time of the return of the year, at the time when kings go out to battle , that Joab led forth the army, and wasted the country of the children of Ammon, and came and besieged Rabbah. But David tarried at Jerusalem. And Joab smote Rabbah, and overthrew it.

And it came to pass after the course of a year, at the time that kings go out to battle, Joab gathered together an army and the strength of the troops, and wasted the land of the children of Ammon: and went and besieged Rabba. But David stayed at Jerusalem, when Joab smote Rabba, and destroyed it.

And it came to pass at the time of the return of the year, at the time when kings go forth, that Joab led forth the power of the army, and laid waste the land of the children of Ammon, and came and besieged Rabbah. But David abode at Jerusalem. And Joab smote Rabbah, and overthrew it.

And it came to pass, at the time of the return of the year, at the time when kings go out to battle, that Joab led forth the power of the army, and wasted the country of the children of Ammon, and came and besieged Rabbah. But David tarried at Jerusalem. And Joab smote Rabbah, and overthrew it.

And it cometh to pass, at the time of the turn of the year, at the time of the going out of the messengers, that Joab leadeth out the force of the host, and destroyeth the land of the sons of Ammon, and cometh in and beseigeth Rabbah, David is abiding in Jerusalem, and Joab smiteth Rabbah, and breaketh it down.

Now in the spring, at the time when kings go out to war, Joab went out at the head of the armed forces and made waste all the land of the Ammonites and put his men in position before Rabbah, shutting it in. But David was still at Jerusalem. And Joab took Rabbah and made it waste.

Now it happened that, after the course of a year, in the time when kings usually go forth to war, Joab gathered an army with experienced soldiers, and he laid waste to the land of the sons of Ammon. And he continued on and besieged Rabbah. But David was staying in Jerusalem when Joab struck Rabbah and destroyed it.

This chapter, containing such other warlike exploits belonging to David's reign as the writer of Chronicles thinks it important to put on record, is to be compared with the passages of Samuel noted in the marginal references.

After the year was expired, at the time that kings go out to battle - About the spring of the year; see the note on 2-Samuel 11:1.
After this verse the parallel place in Samuel relates the whole story of David and Bath-sheba, and the murder of Uriah, which the compiler of these books passes over as he designedly does almost every thing prejudicial to the character of David. All he states is, but David tarried at Jerusalem; and, while he thus tarried, and Joab conducted the war against the Ammonites, the awful transactions above referred to took place.

And it came to pass, that after the year was expired, at the time that kings go out [to battle], Joab led forth the power of the army, and wasted the country of the children of Ammon, and came and besieged (a) Rabbah. But David tarried at Jerusalem. And Joab smote Rabbah, and destroyed it.
(a) Which was the chief city of the Ammonites.

See Gill on 1-Chronicles 20:1, 2-Samuel 11:1, 1-Chronicles 20:2, 2-Samuel 12:30, 2-Samuel 21:15, and 1-Chronicles 21:1.

Though the Lord will severely correct the sins of his believing people, he will not leave them in the hands of their enemies. His assistance will overcome all advantages of number and strength of those that defy his Israel. All that trust in Christ, shall be made more than conquerors through him that loveth them.

RABBAH BESIEGED BY JOAB, SPOILED BY DAVID, AND THE PEOPLE TORTURED. (1-Chronicles 20:1-3)
at the time when kings go out to battle--in spring, the usual season in ancient times for entering on a campaign; that is, a year subsequent to the Syrian war.
Joab led forth the power of the army, and wasted the country . . . of Ammon--The former campaign had been disastrous, owing chiefly to the hired auxiliaries of the Ammonites; and as it was necessary, as well as just, that they should be severely chastised for their wanton outrage on the Hebrew ambassadors, Joab ravaged their country and invested their capital, Rabbah. After a protracted siege, Joab took one part of it, the lower town or "city of waters," insulated by the winding course of the Jabbok. Knowing that the fort called "the royal city" would soon fall, he invited the king to come in person, and have the honor of storming it. The knowledge of this fact (mentioned in 2-Samuel 12:26) enables us to reconcile the two statements--"David tarried at Jerusalem" (1-Chronicles 20:1), and "David and all the people returned to Jerusalem" (1-Chronicles 20:3).