The firing of Katyusha rockets into Israel from south Lebanon this morning was not unexpected, given that the volatile border between the two countries tends to heat up during periods of heightened Israeli-Palestinian violence, but it is unlikely at this stage that it signals the beginning of a new confrontation between Israel and the militants of Lebanon’s Shia Hezbollah.

No claim of responsibility has been made for the rocket salvo, although Palestinian militants — possibly with the tacit blessing of Hezbollah — are the most likely culprits. The Lebanese Government has opened an investigation into the incident and the army in southern Lebanon is on full alert.

Hezbollah, which fields a powerful military wing that fought the Israeli army to a standstill in the month-long war of summer 2006, has little to gain from opening a new front with Israel at this stage.

It is currently rebuilding and expanding its military capabilities, a process that began the moment the ceasefire ended fighting with Israel on August 14, 2006. The organisation has mounted a massive recruitment, training and re-armament drive, unprecedented in scale since Hezbollah emerged in Lebanon more than two decades ago.

Israel says that Hezbollah’s arsenal of rockets, some with an estimated range that brings southern Israel within reach, has tripled since the end of the 2006 war.

Sheikh Hassan Nasrallah, Hezbollah’s charismatic leader, warned Israel today that his organisation was “prepared for every possibility and ready for all aggression”.

“The Zionists will discover that the war they had in July [2006] was a walk in the park if we compare it to what we’ve prepared for any new aggression,” he said.

So far, Hezbollah has restricted its support for its Palestinian ally Hamas to speeches and demonstrations in Beirut rather than military attacks on Israel.

In June, Lebanon goes to the polls in what is expected to be a tense and closely fought parliamentary election. An electoral win for Hezbollah and its allies against the Western-backed parliamentary majority block will strengthen its determination to hold onto its weapons and continue the struggle against Israel.

Triggering a potentially devastating fresh war with Israel for the sake of Hamas in Gaza will not sit well with its Shia constituents, let alone other Lebanese, which is a compelling reason for Hezbollah to limit its actions.

However, Hezbollah will not want to see Hamas and other militant Palestinian groups in Gaza and the West Bank crushed to the extent that they can no longer mount armed resistance against Israel. If Hamas looks to be facing defeat, it is possible that Hezbollah will come to its assistance from Lebanon.

Instead of blindly firing rockets into Israel, Hezbollah might attempt to shoot down Israeli jets that fly in Lebanese airspace on a near daily basis in defiance of United Nations Security Council resolutions.

The downing of an Israeli aircraft by Hezbollah would be considered a “red line” by Israel, but Hezbollah could argue with some justification that its action was a legitimate defence of Lebanese sovereignty rather than an act of aggression against Israel.

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