Level 1 — Absolute Beginner

On Sunday, September 20, 2026, Iran put its army on the highest alert. The alert is called "Code 100." It means the army must be ready for an attack at any time.

The alert covers three groups. They are the Revolutionary Guard, the regular Army, and the security police. All of these groups are now ready for a possible attack.

Iran's military said that a new attack by the United States would get a strong answer. Iran said it would hit back at American bases and friends of the United States.

The United States also sent a warning. It told Americans in the Middle East to be careful. Flights might stop, and airports might close.

alert

a warning to be ready for danger

army

a large group of soldiers that fights for a country

attack

a violent action against a person or place

ready

prepared to do something right away

order

an instruction that must be followed

strong

having great power or force

warning

words that tell people about a danger

careful

paying close attention to avoid danger

Level 2 — Elementary

Iran raised its armed forces to the highest level of alert on Sunday, September 20, 2026. The alert is known as "Code 100," and it is only used when an attack seems close.

The order covers Iran's three main forces: the Islamic Revolutionary Guard Corps, the regular Army, and the country's security forces. All three groups were told to prepare for possible fighting.

Iran's central military command spoke on state television. It said that if the United States or its allies launched a new attack, Iran would strike back at American bases and at any country that helped the attack.

The alert came soon after Houthi fighters in Yemen, who are supported by Iran, fired a missile toward Riyadh, the capital of Saudi Arabia. Tensions in the region have been rising for months.

The U.S. State Department issued its own warning on Saturday. It told American citizens in the Middle East to stay alert, watch for flight cancellations, and expect possible airspace closures.

alert level

a stage that shows how ready a military must be

armed forces

a country's military groups, including the army and navy

command

the group of leaders who give military orders

strike back

to attack after being attacked first

ally

a country or group that helps another in a conflict

tension

a feeling of worry caused by a possible conflict

citizen

a person who legally belongs to a country

cancellation

the act of stopping something planned, like a flight

Level 3 — Intermediate

Iran placed its armed forces on "Code 100," the country's highest state of military readiness, on Sunday, September 20, 2026, amid mounting fears that the United States and its allies could be preparing a fresh assault.

The alert, which is reserved for situations in which an attack is considered imminent, applies across the Islamic Revolutionary Guard Corps, the regular Army, and Iran's broader security forces, putting the entire military apparatus on a war footing.

Speaking through state media, Iran's central military command warned that any new strike would trigger sustained retaliation against American bases and interests, and it cautioned that Washington's regional allies would be treated as participants in the conflict if they took part.

The escalation followed a missile attack on Riyadh by Iran-backed Houthi rebels in Yemen, the first time Saudi Arabia's capital itself had been targeted since fighting in the region intensified again this year, and it unfolds against the backdrop of a broader conflict between the United States, Israel, and Iran that began with strikes in February 2026.

The U.S. State Department added to the sense of alarm on Saturday, issuing a security alert that urged Americans across the Middle East to exercise heightened vigilance, warning of possible flight cancellations and sudden airspace closures if the situation worsened.

readiness

the state of being fully prepared for action

imminent

about to happen very soon

apparatus

a complex system or set of organizations set up for a purpose

retaliation

an action taken to pay back a previous attack

escalation

a rapid increase in the seriousness of a conflict

intensify

to become or make something stronger or more extreme

vigilance

careful attention paid to possible danger

participant

a person or group taking part in something

Level 4 — Advanced

Iran activated "Code 100," its highest level of military preparedness, on Sunday, September 20, 2026, as officials in Tehran voiced growing alarm that Washington and its regional partners might be assembling the groundwork for a renewed offensive.

The designation, reserved for circumstances in which an attack is judged imminent, was extended simultaneously across the Islamic Revolutionary Guard Corps, the conventional Army, and the country's internal security services, effectively placing the entirety of Iran's defense establishment on a war footing.

In a statement carried by state media, Iran's central military command cautioned that any further act of aggression would be met with sustained retaliation against American installations and interests in the region, and it warned that any government assisting such an operation would itself be regarded as a party to the conflict.

The move follows a missile strike on Riyadh by Iran-aligned Houthi forces in Yemen, marking the first time the Saudi capital itself has come under direct fire since hostilities in the wider region reignited this year, and it unfolds against the backdrop of an unresolved war between the United States, Israel, and Iran that has simmered since coordinated strikes in February 2026.

Compounding the sense of crisis, the U.S. State Department issued its own advisory on Saturday, urging American citizens throughout the Middle East to exercise heightened caution and to anticipate the possibility of abrupt flight cancellations and airspace closures should the standoff deteriorate further.

preparedness

the quality of being ready for a possible emergency

designation

an official name or classification given to something

aggression

hostile or violent behavior directed against another party

installation

a military base or facility set up for a specific purpose

hostilities

acts of warfare between opposing groups

reignite

to cause a conflict or feeling to start again

unresolved

not yet settled or brought to an end

standoff

a situation in which opposing sides cannot make progress against each other