Shin Bet, which determined that while it was impossible to stop every single suicide bomber, suicide bombings could be stopped by directly attacking the conspiratorial infrastructure behind them by killing operational commanders, recruiters, couriers, weapons procurers, maintainers of safehouses, and smugglers of money which financed the bombings. Israel was criticized for the use of helicopter gunships in urban assassinations, which often resulted in civilian casualties. Israel criticized what it described as a practice of militant leaders hiding among civilians in densely populated areas, thus turning them into unwitting human shields. Throughout the Intifada, the Palestinian leadership suffered heavy losses through targeted killings. The practice has been widely condemned as extrajudicial executions by the international community, while the Israeli High Court ruled that it is a legitimate measure of self-defense against terrorism. Many criticize the targeted killings for placing civilians at risk, though its supporters believe it reduces civilian casualties on both sides. In response to repeated rocket attacks from the Gaza Strip, the Israeli Navy imposed a maritime blockade on the area. Israel also sealed the border and closed Gaza's airspace in coordination with Egypt, and subjected all humanitarian supplies entering the Strip to security inspection before transferring them through land crossings. Construction materials were declared banned due to their possible use to build bunkers. The blockade has been internationally criticized as a form of "collective punishment" against Gaza's civilian population. Although Israel's tactics also have been condemned internationally, Israel insists they are vital for security reasons in order to thwart terrorist attacks. Some cite figures, such as those published in Haaretz newspaper, to prove the effectiveness of these methods (Graph 1: Thwarted attacks (yellow) vs successful attacks (red) – Graph 2: Suicide bombing within the "green line" per quarter). International involvement The international community has long taken an involvement in the Israeli–Palestinian conflict, and this involvement has only increased during the al-Aqsa Intifada. Israel currently receives $3 billion in annual military aid from the United States, excluding loan guarantees. Even though Israel is a developed industrial country, it has remained as the largest annual recipient of US foreign assistance since 1976. It is also the only recipient of US economic aid that does not have to account for how it is spent. The Palestinian Authority receives $100 million annually in military aid from the United States and $2 billion in global financial aid, including "$526 million from Arab League,