Tall brick raised beds need what sort of base?

I have purchased some jumbo Norman cored bricks for raised beds. One 12x4x32" and one 6x4x32". Do I need to trench a 12in wide x 6in deep and fill with concrete, let age and than start my brick courses? Or can I use tamped down gravel with cement and sprinkled and left to set. I had been planning on putting re-bar supports through the cores since the wall is so tall and I'm NOT doing a double skin. Do I need to do both supports and re-bar OR just one or the other?