Severance of diplomatic relations is a unilateral diplomatic measure short of war, in which a state withdraws its diplomatic mission, expels the other state's accredited diplomats, and ceases official bilateral communication through normal channels. It is distinct from non-recognition (which denies a state's legal existence) and from a rupture of consular relations, which may continue separately under the Vienna Convention on Consular Relations.
The legal framework is set by the Vienna Convention on Diplomatic Relations (1961). Under Article 45, even when relations are severed, the receiving state must respect and protect the premises, property, and archives of the sending mission, and the sending state may entrust its interests and those of its nationals to a third state acceptable to the receiving state — the protecting power arrangement. This allows practical bilateral business (visas, consular protection, sometimes back-channel messaging) to continue through an interests section hosted in another country's embassy.
States sever relations for varied reasons: armed conflict, assassination or attack on diplomats, recognition disputes over third parties, human rights atrocities, or solidarity with an aggrieved ally. Severance is reversible and often signals diplomatic protest more than permanent estrangement; relations can be restored by mutual consent without renewed recognition, since recognition of the state generally persists.
Severance should be distinguished from related measures on an escalation ladder: declaring a diplomat persona non grata, recalling an ambassador for consultations, downgrading representation (e.g., from ambassador to chargé d'affaires), closing a consulate, or expelling all diplomatic staff. Full severance sits near the top of peacetime diplomatic sanctions, typically just below the suspension of treaty obligations or resort to armed measures.
Example
In January 2016, Saudi Arabia severed diplomatic relations with Iran after protesters stormed the Saudi embassy in Tehran following the execution of Shia cleric Nimr al-Nimr.