Jan 5 (Reuters) - With Israeli troops and Hamas gunmen battling in the Gaza Strip for a third day, following is an overview of the tactics and weapons deployed by both sides.

Q - What are the strategies?

A - Israel and Hamas want to inflict maximal damage on each other. Israel has pledged to stem rocket fire from Gaza on its southern towns. It also wants to pummel the Islamists to a point where they are either unwilling or unable to seek another confrontation with the Jewish state. It has not, however, made a commitment to breaking Hamas's control of the coastal enclave.

By corollary, Hamas, whose ultimate goal is an Islamic state in all of what was Palestine in 1948, could claim a victory by living to fight another day. Israel's offensive faces pressures from international diplomacy and an Israeli election on Feb. 10 -- heavy losses among troops would not be popular with voters.

Q - What is the balance of arms?

A - Israel has among the world's most technologically advanced militaries. Thousands of well-trained regular troops and reservists are inside Gaza or on standby. They benefit from high-tech surveillance and communications equipment and can call on massive firepower from tanks, aircraft and navy gunboats.

Hamas has an estimated 25,000 fighters with small arms and rocket-propelled grenades. Israel says it also has more advanced anti-tank missiles and may have shoulder-fired anti-aircraft missiles capable of hitting helicopters or low-flying planes. Palestinian gunmen say they have prepared a matrix of deadly ground obstacles, from minefields to trenches and booby traps.

Hamas has carried out dozens of suicide bombings in Israel and says its men -- and women -- could resume the tactic now.

Hamas has a stockpile of rockets. Many are improvised from pipes, but some Russian-made Katyushas are more accurate and have landed up to 40 km (25 miles) inside Israel.

Q - What are Israel's tactical advantages?

A - Though Israel's troops withdrew from Gaza in 2005 after 38 years of occupation, its intelligence services have studied the territory extensively, anticipating a showdown with Hamas.

Wary of repeating the setbacks in their 2006 war against Lebanon's Hezbollah guerrillas, in which 157 Israelis died, the army has trained extensively and improved communications. Popular anger among Israelis at some 8,000 rockets and mortars fired into Israel from Gaza, killing 18 people from 2000 until the offensive began, has contributed to motivating the troops.

Israeli commanders have imposed new levels of censorship and information security to prevent leaks from the battlefield which might tip off the Palestinians as to military deployments.

The relatively slow progress of Israel's armed forces in Gaza so far, and their relatively low casualty rate, suggests they are advancing slowly and carefully to avoid being ambushed. They appear to have been entering relatively sparsely-populated areas on the outskirts of major Palestinian population centres, searching homes for Hamas members, and setting up outposts that offer vantage points from which to spot and foil attempted rocket launches.

Q - What are Hamas's tactical advantages?

A - Nothing beats a defender's first-hand familiarity with turf. Hamas can also rely on support from many civilians.

Hamas appears to be trying to draw Israeli forces into heavily populated areas, where warrens of alleyways would make their tanks and some of their air support irrelevant.

Hamas leaders have described the current Gaza combat as a fight to the finish, so the guerrillas' motivation -- already stoked by religious zeal -- is high. The ethos of self-sacrifice can make Islamist guerrillas hard even for superior conventional forces to counter.

The Palestinians also appear set on capturing Israeli troops to add to Gilad Shalit, a soldier seized from across the border in 2006. Success in this, and any Hamas threat to kill captives, could allow the Palestinians to stave off Israel.

Q - What are Israel's tactical disadvantages?

A - Israel's apparent caution in pushing into Gaza could become a liability if it turns troops into static targets.

Aware of pressure from its diplomatic allies, Israel says its forces are exercising all possible effort to avoid causing non-combatant casualties, though U.N. figures suggest at least 25 percent of more than 500 Palestinian dead have been civilians. Any especially heavy loss of civilian dead in one incident, or troop losses, could demoralise soldiers by setting off investigations and recriminations along the chain of command.

Q - What are Hamas's tactical disadvantages?

While it won the 2006 parliamentary election and routed the Gaza forces of the rival Fatah faction the following year, Hamas has far from unanimous popular support. Losses people in Gaza have suffered may not endear Hamas and its policy of firing rockets into Israel to the population at large -- although such sentiment could also turn popular anger against Israel.

Hamas has depended heavily on smuggling through Egyptian border tunnels for both arms, funded by Iranian and Syrian allies, and for supplies for Gaza's population. Israel has struck hard at those routes, threatening Hamas's arsenal and also its ability to satisfy local consumers. (Writing by Dan Williams; additional reporting by Nidal al-Mughrabi; editing by Alastair Macdonald)

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