In Gaza, Hamas has been attacking Israel with mortars (mostly 82mm) and homemade rockets (Kassams) for eight years, in an attempt to kill Jews and destroy Israel. These are two primary goals for Hamas, and feature prominently in their propaganda. Since the first Kassam attack in 2001 (at Israelis inside Gaza), about 6,000 rockets have been fired. There were few attacks (about 300 rockets) when Israel occupied Gaza. But after Israel left in mid-2005, Hamas greatly increased the attacks (about 5,700 rockets and 4,000 mortar shells), because Israeli troops were no longer around to interfere with building and launching rockets.
The attacks have been remarkably ineffective, killing only 37 people (half from rockets, the rest by mortars) in eight years. Hamas has had to fire about 270 rockets or mortar shells for each Israel soldier or civilian they have killed. Israeli counterfire killed or wounded a Palestinian for every three Palestinian rockets or mortar shells fired. One Israeli was killed or wounded for every 40 rockets or mortar shells fired. Israeli fire was much more accurate, with most of the Palestinian casualties being terrorists or others involved in building or firing the rockets and mortars. Hamas has tried to get civilians killed, by storing rockets in residential areas, and forming them from those neighborhoods as well. Although Hamas believes in the concept of "involuntary martyrdom" (getting civilians killed for the cause, even if the victims are not willing), many of its chosen candidates for it are not. So civilians stay away from areas where the rockets are launched, and try to conceal the fact that rockets are hidden under their homes.
Kassams began landing in Israel during late 2001, shortly after the Hamas Palestinian terrorist organization perfected the design. This was the Kassam I, and it was 60mm in diameter, about 31 inches long, weighed twelve pounds and carried a one pound explosive charge. Its range is about three kilometers. Like all the Kassams, you aimed it and hoped for the best. In early 2002, Hamas began firing these at Jewish settlements in Gaza as well. By 2003, larger versions were built. There was the Kassam II, which weighed 70 pounds, is 150mm in diameter and six feet long. It has a range of eight kilometers, and a 11-15 pound warhead. It wasn't until June, 2004, that one of these Kassam rockets actually killed an Israeli. By then, about 200 Kassams had been fired into southern Israel.
Later came the Kassam III, which is 6.7 feet long, 170mm in diameter, has a range of about 12 kilometers, and a warhead of 22-44 pounds. This one weighs about 200 pounds. There are many variations in these designs, and larger rockets have been used as well, including the Kassam IV, with a range of 15 kilometers, and a BM-21 clone, called the Nasser 4, with a range of up to 20 kilometers. Costing only $400 to build, materials for the Nasser 4 rockets are smuggled in via the many tunnels between Gaza and Egypt.
Israel and Hamas arranged for a six month truce in June, 2008. During that truce, Palestinians continued to fire rockets (361) and mortar shells (303) into Israel. When Israel began attacking Hamas and other terrorist targets on December 27th, 2008, the Palestinians increased their rocket attacks. But after peaking at about a hundred fired on the 28th, the number launched has declined with each day. Israeli UAVs, aircraft and jets are constantly over Gaza, seeking out rocket workshops, storage areas and launching sites. But since Israeli troops have not yet moved into Gaza City, Hamas is able to continue firing at least ten rockets a day.
Israel knows that Hamas has been stockpiling an arsenal of rockets in Gaza. Israeli intelligence officials believe Hamas currently has, in Gaza, several hundred factory made BM-21 rockets, each with a range of 20-40 kilometers. They also have some shorter range (six kilometers) B-12 rockets. These are not smuggled in much, because the locally made Kassam II has about the same range. However, the B-12 is more reliable (more reliable trajectory and fuze, so more are likely to land where aimed and explode.)
The B-12 is a 107mm, 42 pound, 107mm, 33 inch long, Russian designed rocket that is very popular with terrorists. This rocket has a range of about six kilometers and three pounds of explosives in its warhead. Normally fired, from a launcher, in salvoes of dozens at a time, when used individually, it is more accurate the closer it is to the target. This 107mm design has been copied by many nations, and is very popular with guerillas and terrorists because of its small size and portability.
The 122mm BM-21s weigh 150 pounds and are nine feet long. These have 45 pound warheads, but not much better accuracy than the 107mm model. However, these larger rockets have a maximum range of 20 kilometers. Again, because they are unguided, they are only effective if fired in salvos, or at large targets (like cities, or large military bases or industrial complexes.)
Meanwhile, up north in Lebanon, Hezbollah have stockpiled over 40,000 factory made rockets, mainly BM-21s brought in from Iran via Syria. This is three times as many rockets as they had in the Summer of 2006, when over 4,000 rockets were fired into northern Israel, killing about fifty people, most of them civilians. Over a thousand Lebanese died from Israeli counterattacks. Hezbollah and Hamas plan to launch a joint rocket attack on Israel eventually. The Israelis have been planning more effective countermeasures, which they have not been discussing openly.