5 May hundreds of Tibetans attacked the camp at Changlo and, for a while, looked close to routing the British before eventually being repulsed by the superior weaponry, suffering at least two hundred casualties. On 7 May a small detachment of infantry arrived from General Macdonald who had been ambushed by the Tibetans at the Karo Pass, nearly east of Gyantse, where four of the men had been killed and thirteen badly wounded. A few days later the camp at Changlo came under siege as the Tibetan "troops had gained control of surrounding villages, and taken to firing miniature lead and copper cannon-balls into the camp from Gyantse Dzong." There were even rumours that the Khory Buryat Gelug priest Agvan Dorzhiev, born not far from Ulan-Ude, east of Lake Baikal, then under Russian control, was in charge of the Lhasa arsenal or even directing operations at Gyantse. He had become one of the 13th Dalai Lama's teachers and was suspected by the British of being a Russian spy. After a flurry of communications between Younghusband and the British authorities in India, Younghusband was temporarily recalled to the Chumbi Valley. Younghusband then returned with more than a hundred mounted soldiers, more than two thousand regular infantry, eight artillery pieces, two thousand laborers and four thousand yaks and mules. They arrived on the 28th of June and lifted the siege of Changlo. Attempts to negotiate a settlement failed, with the Tibetans ignoring threats from Younghusband. Also on 28 June, the nearby "seemingly impregnable" Tsechen Monastery and Dzong was stormed shortly before sunset, after a heavy bombardment by a ten-pound artillery gun. Brigadier-General Macdonald, who had just arrived that day, concluded that Tsechen, which guarded the rear of the Gyantse Dzong, would have to be cleared before the assault could begin. An assault was therefore made on the Gyantse fortress on 5 July and, the following day, after a spirited defence by the Tibetans which lasted until sometime after 2 pm, a heavy artillery bombardment blew a hole in the wall followed by a direct hit on the powder magazine, causing a large explosion after which some Gurkha and British troops manage to climb the rock face, scramble inside, and capture the fort in spite of a heavy hail of boulders and stones thrown down upon them by the few defenders left on what remained of the walls. John Duncan Grant was awarded