In 1856, Thomas George Montgomerie, a British Royal Engineers lieutenant and a member of the Great Trigonometric Survey of India, sighted a group of high peaks in the Karakoram from more than 200 km away. He named five of these peaks K1, K2, K3, K4 and K5, where the K denotes Karakoram. Today, K1 is known as Masherbrum, K3 as Gasherbrum IV, K4 as Gasherbrum II and K5 as Gasherbrum I. Only K2, the second highest mountain in the world, has retained Montgomerie's name. Broad Peak was thought to miss out on a K-number as it was hidden from Montgomerie's view by the Gasherbrum group.