It is no secret that since 2006's war in Lebanon and the 2005 disengagement from the Gaza Strip, Hizbullah and Hamas have been engaged in two of the most intensive military buildups in the world. Hizbullah, according to Israeli intelligence, has tripled its missile arsenal and today has more than 30,000 rockets and long-range missiles that can hit anywhere in Israel. Hamas has used the three years since Israel's unilateral withdrawal from Gaza to smuggle in thousands of tons of high-grade explosives for its Kassam rockets, roadside bombs and mines, as well as longer-range Katyusha rockets. Despite this massive buildup, the assumption has always been within the defense establishment that the air force would still be able to operate almost freely over both Lebanon and Gaza, where there are neither air forces nor strong anti-aircraft capabilities. This seems to be changing. According to new intelligence assessments presented to the security cabinet on Wednesday, the days that the IAF could fly over Gaza and Lebanon without concern are over. Hamas is believed to have smuggled into Gaza an unknown number of shoulder-to-air missiles as well as heavy anti-aircraft machine guns. For this reason, in December the IAF changed its regulations for flying over the Strip. Now only helicopters equipped with anti-missile defense systems are allowed to fly over Gaza. The aircraft hover at a significant, undisclosed altitude as an additional precaution. Last month, The Jerusalem Post reported exclusively on how, according to foreign sources, the Iranian and Syrian militaries were assisting Hizbullah in installing advanced radar installations atop the Sannine Mountains in Lebanon's Bekaa Valley that can be used to track IAF planes from the Mediterranean Sea in the west to Damascus in the east. The assumption within Israel has always been that anything Syria has in its storehouses would also wind up one day in Hizbullah hands. Since the Second Lebanon War - when one helicopter was shot down - the defense establishment has become more confident in its assessment that the systems are already there. Hizbullah and Hamas are not the only ones busy enhancing their anti-aircraft capabilities. Syria and Iran have both held talks with Russia on the S-300 anti-aircraft system and recent news reports have claimed that the system will arrive in Iran by the end of the year. The S-300 is one of the best multi-target anti-aircraft-missile systems in the world today and has a reported ability to track up to 100 targets simultaneously while engaging up to 12 at the same time. Syria recently received 36 Pantsir S1E air-defense systems from Russia, which have a range of 12 kilometers. These countries and terror groups are investing in anti-aircraft systems due to an understanding that the IAF is the strongest air force in the region and that they will not likely build an effective airborne challenge to it in the foreseeable future, meaning that the only way to counter the IAF is with ground-to-air missiles. These systems - in Gaza, Lebanon, Syria and Iran - do not make Israeli missions impossible but they do make them more complicated. The IAF is compelled to be extra-careful when flying in these areas since the skies are no longer clear for Israel.