Some context: Tedder was born the son of Sir Arthur John Tedder and Emily Charlotte Tedder (nee Bryson) at the Glenguin Distillery (now Glengoyne) in the Campsie Fells, north of Glasgow. His father was distinguished as the Commissioner of the Board of Customs who devised the old age pension scheme. His father's occupation meant that the young Tedder saw different parts of the British Isles, spending 1895 to 1898 in Lerwick on the Shetland Isles and 1899-1901 in Elgin, in the County of Moray. In 1902 the family moved to Croydon in Surrey and Tedder attended the Whitgift School until 1909, when he went up to the University of Cambridge.
Tedder was promoted to lieutenant in the Dorset Regiment on 14 October 1914, and arrived back in Britain in December. He was posted to a reserve unit at Wyke Regis on the Dorset coast where he seriously injured his knee in February. Following his injury Tedder was unable to carry out full infantry service and, although he briefly carried out duties at a base camp in Calais, he pressed for a transfer to the Royal Flying Corps.  In January 1916, Tedder was accepted into the Royal Flying Corps and he was asked to attend the No. 1 School of Aeronautics. in Reading. He was promoted to captain on 21 March 1916. In April he attended the Central Flying School where he learned to fly and gained his 'wings'. In June 1916, Tedder served as a pilot with No. 25 Squadron RFC flying the Bristol Scout C on the Western Front. On 9 August 1916, Tedder was given additional responsibilities as he was made a flight commander with 25 Squadron. The first day of 1917 saw Tedder promoted to major and appointed officer commanding No. 70 Squadron RFC. Tedder remained on the Western Front and his new squadron was equipped with the Sopwith 1 1/2  Strutter. He was awarded the Italian Silver Medal for Military Valour on 26 May 1917.  Tedder was appointed officer commanding No. 67 Squadron at RFC Shawbury on 25 June 1917 and became commander of the School of Navigation and Bomb Dropping in Egypt the following year. Another change soon followed and on 24 June 1918 Tedder was appointed officer commanding 38th Wing, also based in Egypt. He was promoted to the temporary rank of lieutenant colonel on 23 July 1918 (rank relinquished on 2 April 1919).
How did he hurt his knee?
A: 
Some context: Emiliano Zapata Salazar (Spanish pronunciation: [emi'ljano sa'pata]; 8 August 1879 - 10 April 1919) was a leading figure in the Mexican Revolution, the main leader of the peasant revolution in the state of Morelos, and the inspiration of the agrarian movement called Zapatismo. Zapata was born in the rural village of Anenecuilco in Morelos State, where peasant communities were under increasing pressure from the small landowning class who monopolized land and water resources for sugar cane production with the support of dictator Porfirio Diaz. Zapata early on participated in political movements against Diaz and the landowning hacendados, and when the Revolution broke out in 1910 he was positioned as a central leader of the peasant revolt in Morelos. Cooperating with a number of other peasant leaders he formed the Liberation Army of the South of which he soon became the undisputed leader.
In mid-March 1919, Gen. Pablo Gonzalez ordered his subordinate Col. Jesus Guajardo to commence operations against the Zapatistas in the mountains around Huautla. But when Gonzalez later discovered Guajardo carousing in a cantina, he had him arrested, and a public scandal ensued. On March 21st, Zapata attempted to smuggle in a note to Guajardo, inviting him to switch sides. The note, however, never reached Guajardo but instead wound up on Gonzalez's desk. Gonzalez devised a plan to use this note to his advantage. He accused Guajardo of not only being a drunk, but of being a traitor. After reducing Guajardo to tears, Gonzalez explained to him that he could recover from this disgrace if he feigned a defection to Zapata. So Guajardo wrote to Zapata telling him that he would bring over his men and supplies if certain guarantees were promised. Zapata answered Guajardo's letter on April 1, 1919, agreeing to all of Guajardo's terms. Zapata suggested a mutiny on April 4. Guajardo replied that his defection should wait until a new shipment of arms and ammunition arrived sometime between the 6th and the 10th. By the 7th, the plans were set: Zapata ordered Guajardo to attack the Federal garrison at Jonacatepec because the garrison included troops who had defected from Zapata. Pablo Gonzalez and Guajardo notified the Jonacatepec garrison ahead of time, and a mock battle was staged on April 9. At the conclusion of the mock battle, the former Zapatistas were arrested and shot. Convinced that Guajardo was sincere, Zapata agreed to a final meeting where Guajardo would defect.  On April 10, 1919, Guajardo invited Zapata to a meeting, intimating that he intended to defect to the revolutionaries. However, when Zapata arrived at the Hacienda de San Juan, in Chinameca, Ayala municipality, Guajardo's men riddled him with bullets.  After he was gunned down, they then took his body to Cuautla to claim the bounty, where they are reputed to have been given only half of what was promised. Zapata's body was photographed, displayed for 24 hours, and then buried in Cuautla. Pablo Gonzalez wanted the body photographed, so that there would be no doubt that Zapata was dead: "it was an actual fact that the famous jefe of the southern region had died." Although Mexico City newspapers had called for Zapata's body to be brought to the capital, Carranza did not do so. However, Zapata's clothing was displayed outside a newspaper's office across from the Alameda Park in the capital.
When did Zapata die
A:
On April 10, 1919,