When is a ceasefire not a ceasefire?

Last week, after a year-long, unilateral ceasefire had been announced by Hamas following negotiations with Egypt, a Hamas spokesman clarified that it is not an actual ceasefire, a hudna, meaning a complete cessation of hostilities, rather it is a calming or tahadiya, meaning that Hamas can break the ceasefire any time they please.
On Tuesday under cover of fog they hid several bombs along the border and when an IDF patrol passed nearby they were detonated, killing a Beduin tracker and injuring an officer. In response, the IAF carried out a raid that killed a man on a motorbike, supposedly one of the bombers, and another Palestinian, supposedly a farmer. Hamas' excuse for this bombing was that Israel has not adhered to its conditions for a full ceasefire, namely it has not fully opened the border crossings. Wednesday the terrorists also fired two mortars into southern Israel, and Israel in return closed all the crossings. The security cabinet met to decide how to respond. Now that Israel is intent on confirming its deterrence and there is an election campaign underway they are likely to respond strongly. It was announced by FM Tzipi Livni that the former policy of restraint enunciated by Defense Minister and Head of Labor Ehud Barak is over.
Also Tuesday George Mitchell, special envoy of Pres. Obama, visited Pres. Mubarak in Egypt and will arrive in Israel Wednesday to meet all the usual suspects. During an interview with Al Arabiya TV Pres. Barak said yesterday that on this trip he had asked Mitchell only to listen, not to suggest any US initiatives. After his tour, when he returns to Washington, he and Mitchell will meet and discuss options.
It is evident that Obama is earnest in his intentions to take the Middle East situation seriously early in his term. But, maybe he has bitten off more than he can chew. Perhaps Bush was right, that publicly committing a President to a difficult and dangerous situation so early on can damage his credibility, since no early positive outcome is expected. Now that Hamas have breached the truce, while everyone is talking of the need for a "durable" ceasefire, only shows how precarious things are. Also, a conference is arranged for next week in Copenhagen to discuss how to prevent the smuggling of arms into Gaza. Clearly noone would be taking these matters seriously if Israel had not finally tired of the rocketing of its civilians and counter-attacked.