I wrote a reply a month ago in an AMA in response to a similar question. Broadly speaking, the mid-to-late 15th century is usually seen as the time when standing professional armies started to emerge in Western Europe. Pre-existing forces in France and Burgundy were reorganized into companies under more centralized control. The Iberian monarchs Ferdinand and Isabella also started to develop a more centralized military apparatus, which coincided with the centralizing tendencies of their rule in general. I'm not sure exactly what you mean by "bannermen," which is a term I've only ever seen in Game of Thrones. The private retinues and military forces of the aristocracy were faced with increasing regulation in most western European monarchies throughout the late 15th and 16th centuries. This sometimes resulted in civil strife (which I discuss in my replies to the questions in the AMA), but did not always result in a standing army being formed out of the remnants of the old retinues and companies. England lagged significantly behind the military developments of continental Europe throughout the early modern era and lacked a professional army for the entirety of the 16th century, with the possible exception of its naval forces.

Are you referring to lords of a kingdom? Is that what Bannermen are referring too?

Thanks for the awesome answers. I think I might need to stop watching so much Game of Thrones.