Judging by the number of Palestinian casualties, Operation Protective Edge has been far less bloody than the November 2012 and December 2008- January 2009 Gaza operations.Even as critics say Israel is using disproportionate force, there are more international figures than usual noting the Jewish state’s restraint, and some critics are making their criticisms grudgingly more nuanced.But the longer any war goes on, the more mistakes there are. This is because one needs to start hitting riskier targets to continue to have targets to hit, the daily “routine” can wear down caution and, simply, more attacks means more opportunities for mistakes.Between Tuesday to Wednesday, the IDF says it attacked military targets near al-Wafa hospital and on a beach.In these attacks, it appears the IDF tried to warn patients at the hospital to evacuate, but they were unable to leave, and in the beach incident, four Palestinian children were killed.Regarding the hospital, there may have been numerous military targets in the vicinity of the hospital as part of a Hamas human-shield strategy for hiding among civilian areas.It may be that as a general principle, as articulated by an Israel Democracy Institute report released Thursday, that once the hospital area, initially a non-military location, made “an effective contribution to military action,” became a valid military target. Israel, nonetheless, fulfilled its obligation to warn the patients to leave.B’Tselem said the hospital has 17 patients, between the ages of 14 and 95, all suffering from different degrees of paralysis.It added that “there is no other rehabilitative institute in the area where patients can be transferred. These patients require special conditions that cannot be recreated,” implying that a transfer not to a special rehabilitative hospital could be life-threatening.Maybe there is no “effective” warning in such an exceptional situation, and then the proportionality standard for saying that hitting the military targets in the area was greater than the potential civilian loss would be awfully high.Maybe in such an exceptional situation, if the IDF wanted to attack it would need to get the patients to another rehabilitative hospital. Maybe even in Israel? The IDF discussed general principles on the issue, but might not have been ready for such specifics that it ran into in a longer operation.The beach incident seems an evident mistake, not merely because of the killed children, but because the IDF announced, specifically following that incident, that Maj.-Gen. Noam Tibon would be investigating all civilian casualties.Also, the IDF’s explanations were more circumspect, whereas sometimes the IDF defends such incidents unequivocally.Further, visual and written descriptions seem to indicate that the IDF’s normal best defense for indirectly hitting civilians in an urban setting, would not apply – after all this was a beach, not the middle of a city (there appear to be some structures, but not of great density).None of the above proves a mistake, let alone a war crime, but it does prove that the longer the operation runs, the greater mistakes are likely to be with exceptional situations that trump the IDF’s general arguments, and the greater the danger of committing a war crime.