The Independent article contains the phrase (much discussed in other media) that:
"The attack in September saw 15 Taliban fighters dressed in American uniforms walk past an unmanned watch tower"
This reads as if there was a decision not to man the tower in question which left sections of the wire unobserved. If this was true then one might conclude that this was an unacceptable risk taken by commanders against the insurgent threat faced. However, if the towers chosen by those commanders to be manned were sufficient to provide uninterrupted continuous observation of the perimeter fence one would need to consider whether the sentries did not observe the incursion due to a human factor - whether blameworthy or otherwise. In any case perhaps there are degrees of complexity that might reasonably be left to those with all the facts – this is a rumour site but people’s names are in public here and we are normally rightly sensitive about speculation in such cases.