Joined: Apr 2011
From: Oregon, USA
From the Cambridge History of the Byzantine Empire, p. 380, there's this overview of the encounter:
“Mu’awiya and his successors failed to find a single stratēgos or senior officer within the all-important theme of the Anatolikoi who would be willing to betray his command to the Muslims. The best-known example of Muslim attempts to subvert a Byzantine border commander are the negotiations in 717 [my note: year must be wrong, Leo was in Constantinople by then and crowned] between the commander-in-chief of the great expedition against Constantinople, Maslama bin ‘Abd al-Malik, his field commander, Suleiman bin Mu’ad, and Leo ‘the Isaurian’, the wily stratēgos of the Anatolikoi. Leo reportedly parlayed with Suleiman for several days near Amorion. But for all his show of readiness to offer tribute and even reportedly discuss with Muslim emissaries ways of handing the empire over once he had ensconced himself in Constantinople, Leo never intended to submit to the Umayyads: his was a long-drawn-out ruse, as Suleiman and Maslama learned to their bitter regret. These negotiations helped Leo to gain the throne, but they brought only embarrassment and defeat to the Muslims.”
Here's the longer account from Theophanes (extracted from the Turtledove translation), pp. 82-85:
“In this year Maslama attacked Constantinople, sending Suleiman ahead with an army by land and Umar by sea. He marched behind them with a great deal of military equipment. When Suleiman and Bakr reached Amorion, they wrote to Leo the general of the Anaolics: ‘We know the Roman Empire is rightfully yours. Come to us; let us discuss peace terms.’ Suleiman observed that Amorion had no garrison and opposed the general because he backed Artemios. As he wanted to receive Maslama there, he laid siege to it. The Saracens began to acclaim the general Leo as Emperor as soon as he neared the city, and called on those within to do the same. When the Amorians saw that the Saracens were acclaiming him because they liked him, they did so themselves.
“When the general learned that Suleiman intended to destroy the city because it had no garrison or officers, he asked the Arab, ‘If you want me to come to you to discuss peace, why are you besieging this town?’
“Suleiman said to him, ‘Come, and I will withdraw.’ The general got a safe-conduct from him, then came to him with three hundred cavalrymen. When the Agarenes saw him they met him wearing their corselets and full coats of mail; he camped half a mile from their army. He went to them on three days, and they discussed peace terms and the Arabs’ withdrawal from Amorion. The Arabs said, ‘Make peace, and then we will withdraw.’
“The general knew they wanted to seize him. He invited most of the important Saracens to a dinner, but while they were eating Suleiman sent out 3,000 armored Saracens to encircle him and guard him so he could not escape. When his sentries realized this, they told him, ‘A host of Saracen cavalry is surrounding us.’
“One of the Saracens, a cavalryman named Zubayr, came up to him and said, ‘A slave stole a great treasure and fled; that is why our cavalry is in action.’
“The general recognized the tricky ploy; he told them, ‘Do not be distracted. If he should come to our camp we will find him.’
“Although dismayed, through a man of his Leo was secretly able to tell the Amorians, ‘Fear God and do not give yourselves up: learn that Maslama is on his way.’ Their bishop went out to him, and Leo told him the same thing. When Suleiman learned the bishop had gone to him, he sent the general a message: ‘Give us the bishop.’ Because he was surrounded, Leo hid him and told one of Suleiman’s men, ‘After we met he changed clothes and went to the mountains, either through the woods or by the water.’
“When the Arabs made threats about the bishop, the general said, ‘He isn’t here. However, you go off to the emir, and I will come too, and we can talk everything over.’ The Saracens let him go, thinking that when he had come to the emir they would seize him while he was in their midst. He rode off with two hundred men, as if hunting, and gave way to the left. The Saracens with him asked, ‘Where might you be going?’
“He said, ‘I want to shift camp to the springs.’
“They said, ‘Your idea is not a good gone, and we will not come with you.’
“Then the general told his own men, ‘they gave us this safe-conduct because they wanted to seize us, and through us to destroy the Christians. But they will not capture one of our remaining men or horses.’ He kept on going for ten miles and then encamped. On the next day he sent a domesticus who was one of his grooms to the Arabs, whom he told, ‘You gave me a safe-conduct, but you want to capture me by treachery. That is why I have withdrawn.’
“Maslama was coming over the mountain passes, but Suleiman did not know it. His emirs and army rebelled against him: ‘Why are we besieging walls instead of raiding?’ They struck their tents and withdrew.
“Leo sent the turmarch Nikaias into Amorion with eight hundred soldiers and made most of the women and children leave. He himself went to Pisidia.
“When Maslama reached Kappadokia the Kappadokians lost hope for themselves and went out to him, calling on him to accept them. Since Maslama had heard that the Emperor Theodosios hated his general, he wanted to entice Leo and make peace with him, and to subject Romania through him. He asked the Kappadokians, ‘Are you not subjects of this general?’
“‘Yes,’ said they.
“‘Would you do anything if he does it?’
“Then he told them, ‘Go off to your towns, and do not be afraid of anything.’ He commanded his army to do no damage in the general’s provinces. When the general learned this he realized Suleiman had told Maslama he had gotten away from him and withdrawn; he sent letters to Maslama: ‘I wanted to approach you, but when I came to Suleiman he tried to capture me. Now I am afraid to come to you.’
“Maslama told the general’s man, ‘I know the general is playing games with me, because I have not damaged his provinces at all.’
“The general’s man said to him, ‘That is not so; he is writing to you in very truth.’
“Then Maslama asked him, ‘What is the situation in Amorion, which he is near?’
“‘It is well, and under his control,’ he answered.
“Maslama became angry and reviled him: ‘Why should you lie?’
“He said, ‘It is just as I said; Leo has sent troops and a turmarch into Amorion and brought out the superfluous families.’ Maslama was distressed and angered at this, and drove the man away. He had planned to gain control of Amorion during the summer, take over the expedition, and then return to Asia to winter there. Again he interrogated the general’s man, who told him on oath, ‘Everything I have said to you is true, and the turmarch went in there with a thousand troops. Leo removed all the people’s property and the families there without resources.’
“When Maslama heard this he wrote to the general, ‘Approach me; I will make peace, and will do everything you wish.’
“But the general saw that Maslama was near Masalaion, and that in another five days Maslama would have traversed his provinces. He sent out two men of consular rank and told Maslama, ‘I have received your letters and I accept your plan. Behold, I am on my way to you. But as you know, I am a general, and have to have my money and silver and army following me. Send me a safe-conduct for each of them. If affairs turn out as I want of you, well and good: then I will return without penalty and without being put into difficulty.’
“At Theodosiana Maslama told the men of consular rank, ‘I see your general is playing with me.’
“‘Heaven forbid!’ they said."
And finally, here's al-Tabari on Leo's ruse that reportedly convinced Maslama to destroy the Arab food stores outside the city walls, in late summer of 717 (from book XXIV of the SUNY series, Powers' translation, pp. 40-41):
“According to Aḥmad b. Zuhayr - ‘Alī b. Muḥammad: … The Byzantine commanders said to Leo, ‘If you rid us of Maslamah, we will make you emperor.’ And they bound themselves to him by the oath. Then Leo came to Maslamah and said, ‘The people [of Constantinople] know that you will not advance against them in a bold attack and that you intend to prolong the siege as long as you have food. But if you were to burn the food, they would submit.’ So Maslamah burned it. Then the enemy became strong, while the Muslims entered into dire straits until they were on the point of death. This was their situation until Sulaymān died….
“When the Byzantine emperor died, Leo came to [Sulaymān], gave him the news, and assured him that he would deliver the land of the Byzantines [to the Caliph]. So the latter sent Maslamah with Leo, and Maslamah set up camp there, collected all the food around Constantinople, and laid siege to the city. But Leo went to the inhabitants of the city, who made him emperor. He then wrote to Maslamah informing him of what had taken place and asking him to allow enough food to enter the city to feed the people; in this way, the people would believe that his word and Maslamah’s word were one and that they were safe from being captured and expelled from their lands; he also asked Maslamah to give them permission to gather food one night. Meanwhile, Leo had prepared ships and men. Maslamah agreed to his request, and the inhabitants of the city carried away large quantities of food from those enclosures in a single night. At this point, Leo began to act in a hostile manner, having deceived Maslamah by means of a trick that would shame even a woman. The Muslim army suffered what no army had suffered previously, to the extent that a soldier was afraid to leave camp by himself. They ate animals, skins, tree roots, leaves - indeed, everything except dirt. Meanwhile, Sulaymān, who was residing in Dābiq, was unable to send reinforcements due to the arrival of winter. This was the situation until Sulaymān died.”
Hope that helps. It's all I could pull up from my research quickly; there may be more, but those are the primary accounts that I know of off-hand.