If the UK goes to war with Russia, the consequences would be severe and multifaceted. There would likely be a significant military mobilization and escalation, with the UK investing heavily in defense readiness, including modernizing its armed forces and expanding military capabilities in response to what is seen as an immediate threat from Russia. The conflict could involve intense air and missile engagements, with the UK aiming to defend its territory and strike back at key Russian military assets. The war would have major economic implications, including sanctions that have already deprived Russia of substantial war funds, and it would further strain global trade and energy prices. There would also be a high risk of widespread disruption and potential for escalation to more destructive scenarios, including the possibility of nuclear exchange, though this is generally seen as a last and catastrophic outcome.

Military Preparedness and Capabilities

The UK's Strategic Defence Review emphasizes preparing for war-fighting readiness, including renewing its nuclear arsenal and enhancing conventional forces like submarines and aircraft. The Royal Air Force would play a crucial role in intercepting Russian bombers and missiles while launching counter strikes using advanced aircraft such as the F-35B. The conflict would likely begin with intense air and missile attacks aimed at disrupting the UK’s infrastructure and NATO’s front lines.

Economic and Political Impact

Sanctions have already significantly impacted Russia’s war capacity by stripping it of hundreds of billions of dollars in war funds. War with Russia would cause continued economic strain on both sides, disrupting global energy and food prices, exacerbating inflation, and pressuring international trade networks. The UK would need to balance military spending with economic resilience during the conflict.

Mobilization and Societal Effects

In the event of actual war, the UK would likely initiate general troop mobilization, potentially including conscription depending on the scale of the conflict. The government and military intelligence foresee the necessity of engaging the whole population in defense efforts in a total war scenario.

Risks of Escalation

The conflict could either result in a prolonged, costly war with heavy casualties or escalate rapidly into catastrophic devastation, including the possibility of nuclear war, though such an outcome is generally considered a last resort.

National Security Strategy

The UK’s 2025 National Security Strategy underscores Russia as the most acute threat and commits to a "NATO first" defense policy, emphasizing integrated, digitally-enabled military modernization. The strategy stresses a proactive, campaigning approach to defense and security, indicating that any conflict would be comprehensive, involving military, cyber, and diplomatic responses.

In summary, war between the UK and Russia would profoundly affect military, economic, and societal domains, with potentially devastating consequences, extensive mobilization, and a high-risk environment for escalation.