At times of war the art of strategy is to align military means with political ends. However competent the armed forces and brilliant their tactics, if they cannot reach the desired objective then something has to give: the objective must be made more realistic or more means must be found. If neither is possible the result will be frustration, disillusion or even worse. 

At the start of a war, objectives may be set without obvious limit, especially by an aggrieved party seeking to regain what is rightfully theirs or determined to punish a cruel enemy. But what can be achieved depends also on the aims of that enemy and what they can bring to the fight. This challenge of military strategy has become painfully apparent as Israel responds to last weekend’s horrific attacks. It can see no way of negotiating with Hamas and so now wants to defeat it by force of arms, but if it cannot find a way to do so then the cycle of violence will continue.

This need to align ends with means can be seen in the various wars fought by western armed forces in the decades following the end of the cold war, a period in which they enjoyed relative superiority. The US and its allies successfully liberated Kuwait from Iraqi occupation in 1991, carefully avoiding driving to Baghdad to overthrow Saddam Hussein, although leaving him in power meant that he continued to cause trouble. The humanitarian interventions in the former Yugoslavia by western forces were simpler. They were acting in support of a beleaguered people and seeking to deal with the militias that had been oppressing them. In Kosovo in 1999 they confined themselves to using air power.