Siege

A siege was a form of warfare fought by surrounding a fortified position, city or planet.

Major sieges
Jamie McCrimmon watched his elder clansmen fight at the Siege of Quebec. (PROSE: Christmas on a Rational Planet)

The Second Boer War saw the Siege of Mafeking. The First Doctor was present when Mafeking was relieved. (AUDIO: The Barbarians and the Samurai)

At the beginning of World War II, the British Army was surrounded by the Wehrmacht at Dunkirk and faced annihilation, but successful evacuation efforts by sea rescued the bulk of the Allied forces. (PROSE: Timewyrm: Exodus, TV: Co-Owner of a Lonely Heart)

A number of major sieges took place on the war's Eastern Front. The Russian capital city of Leningrad was besieged by the Germans in the Siege of Leningrad. (PROSE: Cabinets of Curosities, Scratchman) Stalingrad was also surrounded in 1942, where the attackers were eventually all captured themselves. (PROSE: The Beast of Stalingrad) Stalingrad was later mirrored at Berlin when the Red Army surrounded and squeezed the Nazis out of the capital. (PROSE: The Shadow in the Glass)

Circa the 25th century, humanity clashed with the Sontarans at the Siege of the Hexion Gates. (PROSE: The Taking of Chelsea 426)

The Siege of Coyote Rock was fought on Vulpana during the Coyote Wars. When the Doctor made a supply run during the siege of Coyote Rock. The whole conflict was later regarded as myth rather than history by Vulpanans of the future. (AUDIO: The Moons of Vulpana)

The Master was found screaming by the the General during the Siege of the Chronotide as the Multiform closed in. (PROSE: Lords and Masters)

The Fall of Gallifrey, the final battle of the Last Great Time War, took the form of a siege when the complete might of the Dalek Empire surrounded Gallifrey, (TV: The Day of the Doctor) and broke through the sky trenches defending Arcadia. (TV: The Last Day) The position of the Dalek Fleet bombarding the planet led to a mass friendly fire incident, the whole fleet blasting itself apart when Gallifrey was pulled out of time to safety. (TV: The Day of the Doctor)

During a Dalek War of the 40th century, Commander Tranter was presumed dead at the Siege of Logario. (COMIC: The Only Good Dalek)

The planet Trenzalore was subject to the Siege of Trenzalore which lasted 900 years. It involved half of all species in the universe and threatened to reignite the Time War. The Eleventh Doctor spent the remaining centuries of his life fighting off the Daleks and other hostile species to defend the town of Christmas. (TV: The Time of the Doctor)

Technology
The Doctor's TARDIS was equipped with a siege mode feature to prevent entry or exit and to protect the vessel when its shields were compromised. (TV: Flatline)