Therefore please make haste if you wish to help us and if you could possibly drive away our assailants, then thanks be to God. But, if not, I, at least, have done my duty; and shortly (for how is it possible to struggle against nature and its imperious demands?) we must bow our heads to necessity and we intend to surrender the fort to the enemy who are pressing us hard and literally throttling us. But if this calamity should eventually come to pass, then may I be accursed! But I now take the liberty of speaking openly to your Majesty.
If you do not hasten with all speed to extricate us from this danger, as we are unable to support the overwhelming burden of warfare, as well as famine, any longer; if you, our Sovereign, do not hasten to bring help when you have the power to do so, then, I say, you will certainly not escape the imputation of betrayal.” From this the Emperor realized that in one way or another he must overcome the foe; and he was oppressed by anxieties and speculations.
And for a whole day during which he invoked the aid of God, he worked hard at the problem of how best to set ambuscades. He also sent for an old man, a native of Larissa, and sought information from him about the lie of the land. With intent eyes and pointing with his finger too, he questioned him carefully about the places where ravines broke through the plain, and whether any thick coppices grew beside them.
Questions of the Larissaean
He asked these questions of the Larissaean because he wished to lay an ambush and defeat the Latins by craft ; for he shirked an open battle in the field as in several engagements he had been worsted and had gained experience of the Frankish method of attack. At sunset, the Emperor, who had toiled all day long, betook himself to sleep and a vision appeared to him. He seemed to be standing in the church of the Protomartyr Demetrius and heard a voice say ” Do not grieve nor groan, tomorrow you shall conquer.”
He thought the voice fell upon his ears from an icon suspended in the temple on which the martyr Demetrius was painted. He awoke full of joy because of the voice of his vision, made his prayers to the martyr and promised besides that, if victory should be granted him, he would travel to Thessalonica and at several stades’ distance  from the town he would dismount and proceed on foot at a smart pace and do obeisance to him in his church. Then he summoned the generals, captains and his relatives and commenced the discussion by asking their individual opinion, and next explained the plan he had formed.
Read More about The Silver Hilt part 3War with the Normans