A dry stream, and the Red Widow
Dunk and Egg take service with a poor old knight in a drought, and find themselves in a small, bitter, entirely typical dispute between neighbours over a dammed stream ÔÇö the kind of quarrel that never reaches a song, and the kind that fills most of a realm's actual history.
The fuller tale
Two years on, Dunk and Egg took service with Ser Eustace Osgrey of Standfast, an old knight with a tower, ten years of grievance, and no men. It was a drought year. The stream that fed his fields had been dammed upriver by his neighbour, and his neighbour was Lady Rohanne Webber of Coldmoat, the Red Widow, who had buried four husbands and was rumoured to have helped some of them along.
There is no war in it. There is a dam, a dead flock, a quarrel about water rights, and an old man who has been telling himself a version of his own past that turns out not to survive contact with anybody who was there. Ser Eustace fought on the wrong side at the Redgrass Field, and everything about his tower ÔÇö the empty stables, the missing sons, the checkered lion he is not supposed to fly ÔÇö comes from that.
It is settled by a marriage and a small amount of blood, and nobody outside two households ever hears of it.
The history nobody writes down
This is the most useful entry in the whole chronicle for understanding what Westeros actually is. The great events fill the books; the realm is mostly this. Two minor houses, one stream, a dispute over water that the losing side can neither win nor let go of, and consequences of a rebellion twenty years dead still working themselves out in a field nobody has heard of.
For every Redgrass Field there were a thousand dry streams, and the men who fought over them thought their quarrel was the important one. They were not entirely wrong.
Elsewhere in the wiki
 See the world as it stood in 211 AC What became of it  if an ending is written, it is here. Spoilers.
The chronicle records no ending here ÔÇö or none the maesters have set down.