When elite Israeli troops crossed into Lebanon to clear booby-trapped Hezbollah positions along the border this week, they expected little resistance. Instead, they found fighters waiting for them with mortars and anti-tank weapons.
These small, cautious incursions have proved relatively costly to the army, a warning to Israel of the heavy fighting that awaits any major operation.
In the Palestinian territories, the army comes up against an enemy armed with little more than Kalashnikovs.
Hezbollah, by contrast, has a well-quipped arsenal: its 2,000-5,000 men have access to missiles, artillery, anti-aircraft guns, and anti-tank weapons.
And there are surprises, such as the Chinese-designed Silkworm cruise missile which appears to have struck an Israeli warship.
When Israel invaded Lebanon in 1982, it lost an estimated 675 soldiers. Israel has fought this war so far almost exclusively from the air. When it has gone in on the ground, even on a limited basis, it has taken casualties.
On Wednesday, two soldiers were killed and nine were injured in fighting over the border from Avivim.
On Thursday, another four were killed by mortar fire, and five were injured in prolonged clashes near the same Lebanese town of Maroun al-Ras.
If Israel is intent on clearing a 1.5km-wide zone in southern Lebanon, it may require the deployment of large numbers of troops a long way further, perhaps up to the Litani river, 20km inside Lebanon, or even beyond.
Hezbollah has two basic options if Israeli troops cross the border in force: attack, an option that would be bloody for the army but even bloodier for Hezbollah; or retreat, redeploy, and return to mount a hit-and-run campaign.
Antony Cordesman, a military analyst at the Washington-based Center for Strategic and International Studies who is familiar with Hezbollah, predicts the latter. He described a ground invasion as "a recipe for a low level war of attrition that neither side can win."
Jonathan Eyal, director of studies at the London-based Royal United Services Institute, said that in such a war, the price would be higher for the army.
"The question is, how much Israelis are prepared to pay for this buffer zone in terms of hand-to-hand fighting? I am not sure that Israel is prepared to pay the price," he said.
"That is the reason they have been so so slow to move in, the reason they have been so cautious. They are desperate to avoid as many casualties as possible. They want to avoid shattering the consensus [of support for the war within Israel]," Eyal said.
Eyal said he expected Israel to go into the buffer zone deployed in large columns to minimize the risk of attack, and to bomb villages -- hopefully free of civilians -- rather than engage in street fighting.
Civilians have been warned by leaflets, text messages and recorded Arabic-language hone messages to leave their homes in the south, perhaps in preparation for a major operation.
Fighting on the ground with Hezbollah carries a further risk: Syria might be drawn in. The Israel-Lebanon border is small and close to Syria, which is a sponsor of Hezbollah, along with Iran.
Israeli planes have occasionally attacked radar sites and other targets inside Syria since Bashar Assad became president following the death of his father in 2000 -- without any response coming from Syrian forces, an embarrassment for the president.
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