Almost six years after the Second Lebanon War, special Israeli units are preparing to take part in mass incursions into Lebanon if another round of fighting with Hezbollah breaks out. Just as important, they are being trained to heed the legal implications.

Officers say the Israel Air Force would destroy targets like training bases and rocket-launching pads within a few days, based on the intelligence gathered by the Israel Defense Forces. But this would not be enough, so a ground offensive would be necessary.

"When you stick an [Israeli] flag [on enemy territory], there's no question who won," says a high-ranking officer who requested anonymity. "You need to seize a geographic space. This is the only way the concept of victory can be established."

The IDF has been trying to improve its performance if hostilities resume, but so has Hezbollah. The Shi'ite organization has built fortified lines with underground command posts and improved operational capacity. Its rockets are hidden in better-camouflaged launching pads.

The ground forces are therefore expected to contribute much more to the war effort than in 2006, when Israel relied mainly on the IAF. This would entail much more intense urban warfare, with many civilians caught in the crossfire, and the attendant legal implications.

"Everything that we've seen with the flotillas, Operation Cast Lead and the implications in terms of international law have left a strong impression on us," says Lt. Col. Sahar Abergil, commander of the special elite unit Yahalom. That unit specializes in bunker warfare and is likely to carry much of the military burden.

"I hope we'll take [international law] into account during the fighting," Abergil says.

Yahalom soldiers, along with the men and dogs of the IDF's Oketz canine unit, finished a long training session last week.

"It's not patrols or raids on Palestinians we're simulating here, but a full-fledged war," says Oketz's commander, who gave his name as Sivan.

One of Oketz's main tasks is to distinguish between militants and uninvolved civilians.

"Our dogs know how to spare civilians and home in on terrorists," says Sivan, a captain. "How do they? That's our secret."

When closing in on a house where the enemy is thought to be hiding, the soldiers must order everyone to exit. Those who don't come out are considered suspects, and the dogs soon get an order to attack.

According to Abergil, "Our goal is that the dogs won't take on civilians. "That's why we include pretend civilians in our drills, to show the soldiers that there are no hard-and-fast rules."

He says the soldiers also discuss moral dilemmas that may have legal ramifications. For example, they are expected to cope if a woman wearing a coat and a little boy approach their post.

"Do they open fire? Do they shout? Do they wound them? Our soldiers understand that it might be a terrorist cynically exploiting a 5-year-old boy, and they're supposed to try to find indications," says Abergil.

"Could she be deaf? Or maybe blind and she's being led by the boy? The army's encounter with a civilian population is never simple, and there's no way to master it fully. We're trying to instruct the soldiers to use their discretion and common sense. At the end of the day, this is war."