1 Chronicles 18:1 - Commentary Critical and Explanatory on the Whole Bible

Now after this it came to pass, that David smote the Philistines, and subdued them, and took Gath and her towns out of the hand of the Philistines. David ... took Gath and her towns. The full extent of David's conquests in the Philistine territory is here distinctly stated; whereas in the parallel passage, 2 Samuel 8:1, it is only described in a general way. Gath was the "Methegammah," or 'arm-bridle,' as it is there called, either from its supremacy, as the capital, over the other Philistine towns, or because, in the capture of that important place and its dependencies; he obtained the complete control of his restless neighbours.