Soon after taking office, several Senators declared that the presence of U.S. military forces in the Philippines was an affront to national sovereignty. Even though Aquino personally felt that they should remain, certain members of the Senate called for the United States military to vacate U.S. Naval Base Subic Bay and Clark Air Base. The United States objected, pointing that they had leased the property and the leases were still in effect. Also, thousands of Filipinos worked at these military facilities and they would lose their jobs and the Filipino economy would suffer if the U.S. military moved out. The United States stated that the facilities at Subic Bay were unequaled anywhere in Southeast Asia and a U.S. pullout could make all of that region of the world vulnerable to an incursion by the Soviet Union or by a resurgent Japan. The Senate refused to back down and insisted that the United States get out even though Aquino herself led a protest against a pullout. The protest gathered between 100,000 and 150,000 supporters, far short of the 500,000 to 1 million that had been originally expected. The matter was still being debated when Mount Pinatubo erupted in June 1991, covering the entire area with volcanic ash. Despite all attempts to continue the Subic Base, Aquino could not get around the Senate's decision. She had to formally concede to it, and in December 1991 the government served notice that the U.S. must close the base by the end of 1992.