What does Judges 9:45 mean?

Abimelech wants to end Shechem and everything in it once and for all. The leaders of the city made him their ruler. They had even helped hire murderers to assist Abimelech in executing his brothers, making him the undisputed heir of Gideon's authority (Judges 9:1–6). It didn't take long for conflict to arise between the two sides, however (Judges 9:22–25). Shechem's leaders wanted him dead and gone. Yet Abimelech had routed them and their puppet leader in battle (Judges 9:38–41). Unsatisfied, Abimelech then ambushed and killed the people of the city who came out to work the fields the next day (Judges 9:42–44).

Even that level of slaughter is not enough for Abimelech. Nor is his goal to force the survivors to serve him or be exiled from their home. Instead, once the field workers are dead, he takes his forces into the city and wreaks havoc. During a day of fierce fighting, he soon captures the city. No prisoners are taken: Abimelech and his men simply murder everyone. They tear down all the buildings in the lower part of the city, leaving the upper area around the temple for later.

In a final act of spite and symbolism, Abimelech "sows" the city with salt. Contaminating fields with massive quantities of salt was a tactic used in ancient times. This was meant to ruin the land's ability to support crops. Eventually, the salted soil would recover, but not before bringing ruin to anyone depending on it for food. Salt was also used as a symbol of agreements and covenants. Scattering salt in and around Shechem may have been a symbolic act to declare that this city would never rise again. Whatever Abimelech does is effective: the city will be empty and barren for almost two hundred years, rebuilt during the time of Jeroboam (1 Kings 12:25).

In the immediate aftermath of the attack, at least one temple remains standing. This is perhaps attached to the defensive tower of Shechem. This will not last long, either (Judges 9:46–49).