The accumulated deterrence achieved in the three previous rounds of widescale fighting in 2008-9, 2012 and 2014 between Israel and Hamas has come temporarily to an end. In retrospect, it was a winning streak, with every round securing greater deterrence. If before the 2008-9 round, Hamas launched on average 1,000 missiles per year, it declined to 400 between the first and second rounds in 2012, to less than 250 between 2012 and 2014, the longest duel between the two sides.Then after the 2014 “the land became quiet for nearly four years” (in the Bible, it was usually 40).Fewer than 80 missiles were launched during that period, most if not all by the wayward Salafi organizations, which is why many of them fell in Gaza itself.There were no casualties and almost no damage from these launchings. The professionals, Hamas, the effective ruler of Gaza, and Islamic Jihad, the organization with real fire power in Gaza, stayed out of the fray.The relative peace changed dramatically after the initiation of the “March of Return” violence at the end of March 2018.It begs the question, why the change, and even more, why is Hamas so far winning the last round of violence hands down after being intimidated for so long? There’s a clear answer. Hamas was finding it increasingly difficult to stave off pressure from thousands of families whose sons were not released in the 2011 Gilad Schalit deal nearly seven years ago. Hamas leaders live in an area where they meet their constituency at every turn, in the refugee camps where many live, in the mosques and in the universities and colleges.Their constituency is not the general public for which Hamas cares little, but part of the hard core of 50,000 or so families in Gaza who support Hamas and Islamic Jihad through thick and thin.The answer to these pressures was the “March of Return” campaign.These were the 20,000 at most who came every Friday afternoon (especially late in the afternoon when the sun blurs the eyesight of IDF soldiers facing it) to the security fence and the few hundreds of those who were willing to put themselves at risk confronting the IDF.Amongst them were the dozens of professional Izzadin al-Qassam troopers, who dashed to, and sometimes through, the fence to destroy any equipment left in the area. They were quickly identifiable by their perfect physiques, purposefulness, agility and speed – Hamas’s crack troops.Twenty thousand at the very most (and probably substantially fewer), the numbers of those subsequently exaggerated by both Hamas and the IDF (the writer was able to more or less count them on the live Hamas al-Aqsa media site). This means that 98.5% of the Gaza population and over 90% of those aged 15 to 35 stayed home, consistently.Worse, the expectations that the residents of the West Bank, Arab Jerusalemites and even Israeli Arabs would do battle with Israeli security forces during the campaign failed miserably. The months that followed were the quietest by far in these arenas since 2013, when terrorism picked up once again in the Jerusalem area and other sites in Israel.Hamas was faced with the question what to do next as not only pressure from the families of the prisoners increased but others in the hard core who wondered why Hamas in Gaza should be the only Hamas adherents to take any risks, especially since they have been paid only 40% of their salaries since 2014.Hamas leaders took a risky decision – to escalate with missiles but in a very selective and limited way. It was very risky because Hamas not only recalled 2014 but it was were facing a new defense minister who talks and acts like Russian President Vladimir Putin and who vowed in the past to destroy Hamas rule in Gaza.The move to escalate was a gamble, and the gamble was won.Limiting the missiles to the Gaza periphery meant that it was possible to increase the costs Israel incurred by not coming to a deal over the prisoners, or alternatively, release more prisoners when Israel comes round to making the deal without risking all-out conflagration.Hamas, experts in Israeli politics, figured that hitting at the 20,000 inhabitants of the Gaza periphery is worth less than a seat in the Knesset during election year.Expanding the strikes to Ashdod, Ashkelon and Beersheba, mainstays of Likud support, would force the Netanyahu government to act in a massive way. This is why Hamas has not struck wider.And this is why the government has responded just as Hamas hoped it would – with limited tit-for-tat strikes in which Israeli civilians and military personnel are increasingly paying a higher price.The answer obviously is that Israel must start preparing for a massive fourth round.There’s simply no other way.The alternative is brokering a prisoner deal which will soon be followed by more rounds of limited Hamas violence to meet other demands – and the list is a long one, from terminating limitations on Gaza fishing (read, enhancing the possibility of arms smuggling from the Syrian coast), or ceasing limiting dual-purpose imports such as cement and steel beams (for underground tunnels and missile storage facilities).Despondent? One needn’t be. The good news is that the fourth round may be like the Yom Kippur War, against the Arab states. There was no change in the level of hatred amongst Arab states in making the decision to end war against the Jewish state. It was sheer pain that made the Yom Kippur War the last in which Arab states actively sought war with Israel.The fourth round might generate the same kind of thinking in Hamas. Its members will no doubt continue to hate the Jews and the Jewish state as before, but the pain might prove to be sufficiently unbearable to induce a change in behavior, though hardly a change of heart.The writer is a Senior Fellow at the Jerusalem Institute for Strategic Studies, Israel’s new conservative security think tank.