The call to Islam was not directed to the leaders only
28-3-2013 | IslamWeb
Question:
As selamu aleykum. In our Islamic history, before muslim armies would attack a foreign land they would give them the options of accepting Islam, paying Jizyah or the sword.These three options were only given to the leadership of the nations and not the masses.Hence, many of the people did not hear the call to Islam and the acceptance or rejection of the leaders was considered binding on the entire population.Could you please tell me the wisdom behind this practice? Jazaakumullahu khayran.
Answer:
All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Islam is the religion of guidance for humanity, aiming to achieve its happiness in this life and the Hereafter. As such, Muslims do not set out to fight anyone or to demand that he pays the Jizyah; rather, they set out to call people to Allaah, both the leaders and those who are led. For more benefit, please refer to Fatwa 83514.
When the Prophet, sallallaahu ‘alayhi wa sallam, dispatched an army, he would command them to first call to Islam. That is the main purpose, as we mentioned above. So they went forth with the goal of calling everyone to Allaah, not only the leaders. Negotiation and dialogue, however, was only possible with some and not all of them; as the custom would be that the leaders represented their people, negotiating on their behalf and holding them to their decision. The Prophet, sallallaahu ‘alayhi wa sallam, thus said in his letter to Heraclius: “If you turn away, then upon you is the sin of the tillers (i.e. by misguiding your peasants).” [Al-Bukhari and Muslim] This means that the one who is followed is responsible for the sins of those who followed him, as he caused them to be misled.
Likewise, the one who followed is sinful for imitating his leader (blindly) without guidance. Allaah the Exalted said: {And they will say, “Our Lord, indeed we obeyed our masters and our dignitaries, and they led us astray from the [right] way.”} [Quran 33:67] It must be known that each one of them is expected to search for the truth; and if he finds it but neglects to follow through with it, then he has no excuse. Instead, he will be held to account for that.
Ibn Hazm 
said (in Al-Ihkaam fi Usool Al-Ahkaam): “The Prophet, sallallaahu ‘alayhi wa sallam, required that only those who heard about his mission believe in him. This included whoever was in the most southern lands and the most northern lands, those in the east, on islands, and in the west, and those in the distant lands of the people of Shirk (i.e. the polytheists): whoever heard of him, sallallaahu ‘alayhi wa sallam, was required to research his status and message and to believe in him...”
As for your statement, “binding upon the entire population”, if you mean that this includes one who comes forth and announces his conversion to Islam, that such would not be accepted from him, then this is not correct. Rather, he will be accepted and will fall under the rulings of Muslims in general. This is what happened with Abu Bakrah 
when he came out from the fortress at Taa’if and announced his conversion to Islam.
Allaah Knows best.