It is not difficult to set up basic guidelines as to determining when a situation has gone too far. Even proponents of Responsibility to protect agree on certain criteria particularly right authority, just cause, right intention, last resort, proportional means and reasonable  Prospects. [1] The last of these criteria will rule out any intervention against a great power such as China where there would not be reasonable prospects of success unless disproportionate means (something like a preemptive nuclear strike) was used. Questions like ‘how many have to die?’ are therefore not asking the right questions because the loss of life could be relatively small (it also assumes that only killing matters) if all the criteria are fulfilled. While this would regrettably constrain any ‘responsibility to protect’ it would at the same time mean that R2P would not become an excuse for starting large scale wars.  [1] Evans, Gareth et al., The Responsibility to Protect, International Commission on Intervention and State Sovereignty, December 2001, p.32