Question: When did Muslim armies invade the country containing Mayer and the country of the man who followed the reign of Al-Mu'tamid?

<P0-S0> Mayer () is a town in northern Syria, administratively part of the A'zaz District of Aleppo Governorate, located northwest of Aleppo. <P0-S1> Nearby localities include Kafr Naya to the northeast and Nubl to the west. <P0-S2> According to the Syria Central Bureau of Statistics, Mayer had a population of 4,772 in the 2004 census. <SEP> <P1-S0> the book of roads and kingdoms (, "kitāb al-masālik w’al- mamālik") is a 9th-century geography text by the persian geographer ibn khordadbeh. <P1-S1> it maps and describes the major trade routes of the time within the muslim world, and discusses distant trading regions such as japan, korea, and china. <P1-S2> it was written during the reign of al-mu'tamid in around 870 ce, while its author was director of posts and police for the abbasid province of djibal. <SEP> <P2-S0> Al-Mu'tadid was the son of al-Muwaffaq, who was the regent and effective ruler of the Abbasid state during the reign of his brother, Caliph al-Mu'tamid. <P2-S1> As a prince, the future al-Mu'tadid served under his father during various military campaigns, most notably in the suppression of the Zanj Rebellion, in which he played a major role. <P2-S2> When al-Muwaffaq died in June 891 al-Mu'tadid succeeded him as regent. <P2-S3> He quickly sidelined his cousin and heir-apparent al-Mufawwad, and when al-Mu'tamid died in October 892, he succeeded to the throne. <P2-S4> Like his father, al-Mu'tadid's power depended on his close relations with the army. <P2-S5> These were first forged during the campaigns against the Zanj and were reinforced in later expeditions which the Caliph led in person: al-Mu'tadid would prove to be the most militarily active of all Abbasid caliphs. <P2-S6> Through his energy and ability, he succeeded in restoring to the Abbasid state some of the power and provinces it had lost during the turmoil of the previous decades. <SEP> <P3-S0> Under al-Mu'tadid he served as commander of the caliph's personal guard and led various expeditions against Bedouins and other restive elements in Iraq, while al-Muqtafi dispatched him in 906 against the Qarmatians. <P3-S1> After al-Muqtafi's death, he played a decisive role in the suppression of the palace coup that briefly deposed al-Muqtadir in favour of Abdallah ibn al-Mu'tazz. <P3-S2> He was then named treasurer ("khazin") and chief of security ("sahib al-shurta") to the Caliph. <P3-S3> He died in 914. <SEP> <P4-S0> The Muslim conquest of the Levant (Arabic: اَلْـفَـتْـحُ الْإٍسْـلَامِيُّ لِـلـشَّـامِ ‎, Al - Faṫṫḥul - Islāmiyyuash - Shām) or Arab conquest of the Levant (Arabic: اَلْـفَـتْـحُ الْـعَـرَبِيُّ لِـلـشَّـامِ ‎, Al - Faṫṫḥul - ʿArabiyyu Lish - Shām) occurred in the first half of the 7th century, and refers to the conquest of the region known as the Levant or Shaam (Arabic: شَـام ‎, 'Syria'), later to become the Islamic Province of Bilad al - Sham, as part of the Islamic conquests. <P4-S1> Arab Muslim forces had appeared on the southern borders even before the death of prophet Muhammad in 632, resulting in the Battle of Mu'tah in 629, but the real invasion began in 634 under his successors, the Rashidun Caliphs Abu Bakr and Umar ibn Khattab, with Khalid ibn al - Walid as their most important military leader. <SEP> <P5-S0> at the beginning of world war i, east prussia became a theatre of war when the russian empire invaded the country. <P5-S1> the russian army encountered at first little resistance because the bulk of the german army had been directed towards the western front according to the schlieffen plan. <P5-S2> despite early success and the capture of the towns of rastenburg and gumbinnen, in the battle of tannenberg in 1914 and the second battle of the masurian lakes in 1915, the russians were decisively defeated and forced to retreat. <P5-S3> the russians were followed by the german army advancing into russian territory.