Spies?

1 Samuel 22 + 23 (various pieces)...

22:1 - When his [David's] brothers and his father's household heard about it...

22:6 - Now Saul heard that David and his men had been discovered.

23:! - When David was told, "Look, the Philistines are fighting against Keilah..."

23:7 - Saul was told that David had gone to Keilah...

23:9 - When David learned that Saul was plotting against him...

23:13 - When Saul was told that David had escaped from Keilah...

23:15 - While David was at Horesh in the Desert of Ziph, he learned that Saul had come out to take his life.

23:19 - The Ziphites went up to Saul at Gibeah and said, "Is not David hiding among us..."

23:25 - Saul and his men began to search, and when David was told about it, he went down to the rock and stayed in the Desert of Maon. When Saul heard this, he went into the Desert of Maon in pursuit of David.

I wonder how each side always heard about where the other was located or what they were up to. In one case it was due to the Ziphite snitches. I wonder if each side had that many spies tracking enemy movement. Or was it just casual observers who relayed information to their leader of choice? There were obviously no fast communication links -- telephones, cell phones, telegraph, spy satellites, emails, U-2 planes, etc. Yet the news did seem to travel rather quickly. I wonder if it was simply the use of fast horses and donkeys that got the job done.