An example of the Prophet (peace and blessings be upon him) consulting his Companions on matters of war.

The Shaykh: And one of the most prominent examples of this is that the Prophet (peace and blessings be upon him), during the Battle of Uhud, when his Companions differed regarding going out to meet the enemy, after he consulted with them and saw that a group of the young men among them were determined to go out, he agreed with them and with meeting the enemy. So when he (peace and blessings be upon him) put on his lamamah, meaning his war clothes such as the armor and helmet and the like, and resolved to go out, those who had advised him to go out wavered. He (peace and blessings be upon him) said: He did not pay attention to their opinion and resolved to fight. The outcome was that Allah (Mighty and Majestic) granted victory to His Prophet and his Companions over the disbelievers. Among the examples of this is that Abu Bakr al-Siddiq (may Allah be pleased with him), when he resolved to fight the people of apostasy, first resolved without consulting any of his Companions, and secondly, after Abu Bakr al-Siddiq opposed him—after 'Umar had opposed him in a logical and theoretical manner, not a practical one, because 'Umar had a doubt—he said: Would you fight a people who testify that there is no god but Allah and that Muhammad is the Messenger of Allah? Abu Bakr al-Siddiq (may Allah be pleased with him) said: Have you not heard the Messenger of Allah (peace and blessings be upon him and his family) say in the hadith that 'Umar cites as evidence: أُمِرْتُ أن أقاتل الناس حتى يشهدوا أن لا إله إلا الله وأن محمد رسول الله ، فإذا قالوها فقد عصموا مني دماءهم وأموالهم إلا بحقِّها It has been narrated on the authority of Abdullah b. 'Umar that the Messenger of Allah said: I have been commanded to fight against people till they testify that there is no god but Allah, that Muhammad is the messenger of Allah, and they establish prayer, and pay Zakat and if they do it, their blood and property are guaranteed protection on my behalf except when justified by law, and their affairs rest with Allah.Sahih Muslim 22. Abu Bakr said to 'Umar: Have you not heard the Messenger (peace be upon him) say, except for its right, the giving of zakah? And these people declared it openly and refused to present the zakah as they used to present it during the time of the Messenger of Allah (peace and blessings be upon him and his family). Therefore, Abu Bakr resolved to fight them and swore by Allah (Mighty and Majestic), saying: "By Allah, if they prevented me from a rope that they used to present to the Messenger of Allah (peace and blessings be upon him and his family), I would fight them for it." Then he fought them, and Allah (Blessed and Exalted is He) granted him victory over them as well.
So, consultation is not obligatory in every matter, but only in matters of worldly affairs where it appears to the ruler that opinion is shared in them. It may be, as it is said, that what is not in the opinion of the preferred one is in the opinion of the less preferred one. He should consult them in such a matter, not in all matters, especially those that are religious matters.