Bonus 'pick and mix' follow-up questions: Was it gradual or sudden? What were your options if you lived outside the walls and bad things started to happen? Was there a formal/legal basis for providing shelter to those that were part of the town but outside the walls, or was it just close the gates and tough luck? Did special laws/rules apply when the town was in a 'gates closed' situation?
The book I own on the Wars of the Roses -- it's at home so I can't cite it -- discusses it for England versus the Continent. He noted that England still saw town walls inland in the 1300s, but by the 1400s they were generally disused. City gates that were built then were light and wide and could not have stood up to cannon -- they were there to collect tolls. The exceptions in England were places that were still exposed to combat: Dover and vicinity, the border with Scotland. (The Continent continued fortifications for much longer because of the combat risk.)
He cited Comneynes (that is HORRIBLY misspelled; a Frenchman who wrote history at the time) saying that this had a major effect on the Wars of the Roses. With no fortifications to hide behind and their possessions exposed, combattants had to seeks a quick decision, which is why each conflict was over so fast and did so little damage. The places where there were sieges (or defensive delays that lasted more than a few hours) were on the Scots border (didn't Edward IV have to capture Berwick three times? Alnwick, &c.), Pembroke (on the edge of Wales), and Calais (combat risk, supra.).