a term used for describing a common method for large expeditions
to conquer a mountain
Siege tactics involves a lot of people, porters, for instance Sherpas, and supporting climbers. These establish routes with fixed ropes and camps further and further up the mountain, and the designated summit climbers climb up and down these routes for practice and acclimatization to the altitude. Bottled oxygen is used and the camps are usually stuffed with food, oxygen and other supplies when the climbers finally go for the summit. These expeditions can include hundreds of people and require a trimmed logistics organization.
These expeditions usually end up in a lot of trash being left on the mountains, since noone wants to carry down all empty oxygen canisters and abandoned tents. The South Col on Mount Everest, from which most summit attempts are made, is often referred to as the world's highest junkyard, 7925 meters, 26,300 feet. Oxygen bottles, tattered tents, frayed ropes, food containers, glass, used syringes and human waste is everywhere here.
As a contrast to this, there's Alpine style climbing.