The United States House of Representatives passed a legislation on Thursday to clear a billion dollars fund attributed to Israel’s popular Iron Dome missile defense system. The vote, which was largely bipartisan in nature, crossed the legislative hurdle with a vote of 420-9.

The news comes as members of the Democratic party moved to quash criticism from Republicans that their party is wavering in support of Israel, a country considered to be a key ally of the United States in the middle east.

A large number of Democratic lawmakers in the House of Representatives sought to place the funding of the Iron Dome in legislation earlier this week in order to remove prevent a government shutdown at the end of the fiscal year, which is September 30.

What is the Iron Dome system?

Iron Dome is an aerial defense system made by Israeli firms Israel Aerospace Industries and Rafael Advanced Defense Systems, along with financial and technical backing from the United States.

The system was first made use of in 2011, and it is developed to stop short-range rockets and artillery like the ones from Gaza. Two different systems called David’s Sling and Arrow, are meant to be used for medium and long-range threats such as planes, drones and missiles.

Iron Dome depends on radar and analysis to understand if an incoming rocket is a threat, while only firing an interceptor if the incoming rocket can potentially attack a populated or an important area. The interceptors are used to detonate the incoming rocket in the air, making it explode in the sky.

The Iron Dome system, which was originally created without assistance from the United States, began receiving funding from Washington DC in 2011. The related expenses for the defense system were estimated to be around $1.6 billion, according to reports from Bloomberg.

According to media reports citing Israel’s Institute for National Security Studies, the cost of each missile is between $40,000 to $50,000.