Protective Edge, the war between Israel and Hamas, has received some legitimacy from key Israeli allies; both the US and Europe have observed Israel's right to defend itself against rockets and terror infiltration through tunnels. But from the start, the life span of that support was bound to be short. As a brief ceasefire was reached on Saturday, it may already be waning.

The reason can be summed up as follows: the immediate casus belli – Hamas aggression – appears to justify Israel's actions. But on closer inspection, threats against civilians fade compared to actual carnage among civilians – Palestinians. Zooming out, the long-term context of the conflict is increasingly indefensible. Yet Israel's argument for the war depends on immediate justifications and ignores the context. To compensate, Israel is fixated on narrative, in the deep conviction that a campaign of slogans and images, known as "hasbara", will work.

Start with the immediate pretext for the war: no one can allow rocket fire at civilians or terrorists' infiltration through tunnels. But many also know that both Israel and Hamas have played the game of provocations leading here. Israel's prime minister, Binyamin Netanyahu, in a double rage following a Hamas-Fatah reconciliation agreement and the murder of three Israeli teens in June, undertook a massive sweep against Hamas in the West Bank (producing no evidence that the latter committed the murders). The move was bound to elicit a reaction.

Wartime realities further erode Israel's case. Ironically, as the Iron Dome system protects Israelis from Hamas rockets, it highlights Palestinian civilians' helplessness. And it is tough to link the aim of destroying tunnels with the bombing of a UN school sheltering those who had fled their homes. Then there's the long view. Protective Edge represents the third war in five years, the umpteenth failure of peace negotiations that Netanyahu never intended would succeed. The international community tolerated Cast Lead, a Gaza war in 2008-9 (at least while it was happening) in part because then-prime minister Ehud Olmert had truly sought for long-term resolution through negotiations and concessions, but failed. Under Netanyahu, Israel's image as a rejectionist is more entrenched than ever.

Israelis hold the opposite view. For them, the last few years were a time of relative calm. They traded suicide bombs of the early 2000s for regular Gaza "operations" with low Israeli casualties, in the firm belief that it cannot be otherwise. They repress Palestinian statelessness and deep constraints on people, movement, goods, livelihood; they believe Gaza is unoccupied. They remember the conflict when Israelis are victims: when youngsters are murdered and rockets are fired.

For Israel, this is a war against Hamas that started a few weeks ago. Outsiders increasingly see it as war against Gaza for years, and against Palestinians for decades. In that environment, it doesn't matter who fired at the UN school.

People were killed because of a war, because of the big picture, which doesn't favour Israel. Not wishing to address the big picture, Israel has embraced hasbara to explain its pinpointed strikes. The strategy fails on multiple levels.

In general, Israeli hasbara observes only those short-term arguments for the war. But it drills down even further, to explain tactics and incidents. The UN school, like other cases before it, could be reduced to a whodunnit in the grimmest of games: Who fired the shot? Did Palestinians doctor the photos? Evidence-doubting is becoming a favourite game.

But as the war heats up, the global media pay closer attention to the whole situation. The world is able to pan out to see the whole picture, while Israel is zeroing in.

Another problem is that hasbara serves up pith instead of policy. From its Twitter account, the IDF offers these formulations: "Hamas does not exist for the people of Gaza; it abuses its people in order to exist."

"Israel uses its weapons to protect civilians; Hamas uses its civilians to protect weapons."

The slogans are augmented by flashy graphics that could grace a magazine but are no substitute for solutions. Netanyahu may know that the cartoon bomb he flashed in his 2012 United Nations speech about the Iranian nuclear threat yielded jokes. This time, no one is laughing.

Worse still, the scent of hasbara taints even clearly legitimate actions. Thus: "IDF soldiers were rushed by a female suicide bomber in Gaza. They were able to neutralise the threat," reads another message. Surely everyone can agree on the need to kill a suicide bomber before she strikes, if necessary. But the euphemistic self-justifications that are so overused in far less clear situations can cause momentary doubt even here.

By ignoring and perpetuating the long-term conflict, obsessively reading only the very, very short term, and by dressing up its actions in cheap linguistic clothes, Israel's communications may backfire among precisely those who need to be convinced.

There are two paths to understanding this conflict – Israel's and those seen by the outside world. Increasingly, they do not cross.

Dahlia Scheindlin is a public opinion researcher and consultant. She lives in Tel Aviv, and writes a regular column for +972 Magazine, an Israeli blog.