of power. But at the same time, Morocco and Mauritania began to put pressure on the Franco government: both countries argued that Spanish Sahara formed a historical part of their own territories. The United Nations became involved after Morocco asked for an opinion on the legality of its demands from the International Court of Justice (ICJ), and the UN also sent a visiting mission to examine the wishes of the population. The visiting mission returned its report on October 15, announcing "an overwhelming consensus" in favor of independence (as opposed to integration with Morocco or with Mauritania, or continued rule by Spain). The mission, headed by Simeon Aké, also declared that the Polisario Front seemed the main Sahrawi organization of the territory - the only rival arrangements to what the mission described as Polisario's "mass demonstrations" came from the PUNS, which by this time also advocated independence. Polisario then made further diplomatic gains by ensuring the backing of the main Sahrawi tribes and of a number of formerly pro-Spanish Djema'a elders at the Ain Ben Tili conference of October 12. On October 16, the ICJ delivered its verdict. To the dismay of both the Rabat and Nouakchott governments, the court found with a clear majority, that the historical ties of these countries to Spanish Sahara did not grant them the right to the territory. Furthermore, the Court declared that the concept of terra nullius (un-owned land) did not apply to the territory. The Court declared that the Sahrawi population, as the true owners of the land, held a right of self-determination. In other words, any proposed solution to the situation (independence, integration etc.), had to receive the explicit acceptance of the population to gain any legal standing. Neither Morocco nor Mauritania accepted this, and on October 31, 1975, Morocco sent its army into Western Sahara to attack Polisario positions. The public diplomacy between Spain and Morocco continued, however, with Morocco demanding bilateral negotiations over the fate of the territory. On November 6, 1975 Morocco launched the Green March into Western Sahara. About 350,000 unarmed Moroccans accompanied by the Moroccan Army armed with heavy weapons converged on the city of Tarfaya in southern Morocco and waited for a signal from King Hassan II of Morocco to cross into Western Sahara. As a result of international pressure, Spain acceded to Moroccan demands, and entered bilateral negotiations. This led to the Madrid Agreement