Having just had a moment of clarity I will add one more thing. Taking the Clausewitzian view of the relationship between warfare and politics, absolutely anything the CDS says can be interpreted politically. He cannot avoid the political sphere precisely because he is part of it. There is a difference between making a factual statement that can be interpreted politically, as CDS did, and entering the realm of party politics; it is Corbyn that has dragged it into the latter through his response to CDS.