Jamieson, Fausset and Brown on 1 Samuel 13:3-4

3-4. And Jonathan--that is, "God-given."

smote the garrison of the Philistines ... in Geba--Geba and Gibeah were towns in Benjamin, very close to each other (Jos 18:24, 28). The word rendered "garrison" is different from that of 1Sa 13:23; 14:1, and signifies, literally, something erected; probably a pillar or flagstaff, indicative of Philistine ascendency. That the secret demolition of this standard, so obnoxious to a young and noble-hearted patriot, was the feat of Jonathan referred to, is evident from the words, "the Philistines heard of it," which is not the way we should expect an attack on a fortress to be noticed.

Saul blew the trumpet throughout all the land--This, a well-known sound, was the usual Hebrew war-summons; the first blast was answered by the beacon fire in the neighboring places. A second blast was blown--then answered by a fire in a more distant locality, whence the proclamation was speedily diffused over the whole country. As the Philistines resented what Jonathan had done as an overt attempt to throw off their yoke, a levy, en masse, of the people was immediately ordered, the rendezvous to be the old camping-ground at Gilgal.

1Sa 13:5. The Philistines' Great Host.