Agree they should all be tried but in practice the best sequence may be to start at the bottom and establish there that crimes took place and have the defences

Agree they should all be tried but in practice the best sequence may be to start at the bottom and establish there that crimes took place and have the defences establish the orders given as mitigation to build that case against the politicians and senior leadership. Having the juniors in prision would build political pressure from those who follow orders (military etc.) for the politicians to join them and hopefully make it less of a party political issue.