Everything that should occur for WW3 to be declared – from international locations concerned to who decides

With fears of World War 3 at their highest in decades due to escalating conflicts in Ukraine, Taiwan, and the Middle East, the Daily Star explains exactly how a UK declaration of war would unfold

View 3 Images

As the ongoing war in Ukraine remains a top concern, with analysts pointing to the risk of a direct clash between Russia and Western nations, tensions between China and Taiwan, mounting conflicts and war in the Middle East, fears of a potential World War 3 have reached new heights.

From the international flashpoints that could trigger war, to exactly who has the authority to declare it, how the public would be notified, what emergency powers the government could invoke, and the practical steps every household should take to prepare, the Daily Star covers every key detail about what would happen if the unthinkable became reality.

Keep on reading to know everything you need to know about a potential declaration of a World War 3:

Who declares war?

According to the UK Parliament’s official website, under Royal Prerogative powers, the Prime Minister (acting on behalf of the Monarch) has the authority to declare war and deploy armed forces. If World War 3 was to be declared now, this role would fall on Sir Keir Starmer.

While a constitutional convention has developed since 2003 where the House of Commons should debate and vote on military action, this is not a legal requirement. In an emergency where a vote is not appropriate, the government can act unilaterally.

How would we know?

The most immediate notification would likely come via the UK Government Emergency Alerts system, the UK Government explains. This sends a message to all compatible smartphones, accompanied by a loud, 10-second siren-like sound and vibration, even if the phone is on silent.

Following historical precedent (like Neville Chamberlain’s 1939 radio broadcast), the Prime Minister would likely address the nation via television and radio. In local areas, authorities might use loudhailers (from cars or helicopters), door-to-door notifications, or electronic message boards on motorways.

What would happen in the UK?

The government can invoke the Emergency Powers Act 1920 (amended in 1964) to declare a State of Emergency. This allows them to take measures to ensure the supply and distribution of food, water, fuel, and transport.

The 2025 National Security Strategy prioritises protecting critical infrastructure (electricity, gas, transport) from cyber-attacks, sabotage, and direct threats. Moreover, experts have suggested that a major conflict could lead to a move toward “warfighting readiness”, which might eventually include the prospect of conscription (the draft) within a few years if professional forces are insufficient.

How many countries involved?

There is no official legal definition or minimum number of countries required for a conflict to be classified as a “World War”. The term is largely descriptive, used by historians and political scientists after the fact, and is based on the scale and impact of the conflict rather than a specific threshold.

Generally, a war is considered a “World War” if it is fought across multiple continents or involves most of the world’s major powers. For example, the First World War involved around 30 nations across Europe, Africa, the Middle East, and Asia, while the Second World War saw over 50 countries fighting across almost every continent and ocean.

A key feature of a World War is the involvement of the world’s dominant military powers, grouped into opposing blocs. In the modern era, a conflict that forces countries to align with blocs led by the US/NATO, China, and Russia would likely be labelled a “World War”, even if only a dozen or so countries were directly fighting.

What side is the UK on?

One mechanism that could rapidly transform a regional conflict into a global one is NATO’s Article 5 – the principle of collective defence. Article 5 states that an attack on one NATO member is considered an attack on all, legally binding all 32 member countries to assist the nation under attack.

However, the treaty is deliberately vague; while it allows for military action, it does not make it automatic. Allies can choose to respond with military force, intelligence sharing, equipment, or sanctions.

As of March 2026, NATO consists of 32 member countries, including the UK, all legally bound by Article 5’s collective defence guarantee. In response to rising tensions, NATO allies have recently agreed to increase defence spending targets to 5% of GDP by 2035, aiming to ensure that the Article 5 commitment remains a credible deterrent in an increasingly uncertain world.

What should people do?

The government’s Prepare Campaign advises households to maintain an emergency kit with nine key items:

• Communication & Light : Battery or wind-up torch, portable power bank, battery or wind-up radio, and spare batteries.
• Supplies : A first aid kit, hand sanitiser/wet wipes, and at least 2.5–3 litres of bottled water per person per day.
• Food : Non-perishable food that doesn’t require cooking (and a tin opener).

In a real emergency, the Emergency Alert message will contain specific instructions (e.g., “stay indoors,” “prepare for evacuation”) that citizens are urged to follow immediately once it is safe to do so

For the latest breaking news and stories from across the globe from the Daily Star, sign up for our newsletters.