It was enough only to look around the centre of the capital, where the tightest security measures were in force three days after the guerrillas launched co-ordinated attacks in six states.
Some 16,000 police joined thousands more army, navy and air force personnel throughout the city to guard the Congress, the city centre, the international airport and key electricity, fuel and water installations. Sharpshooters perched on government buildings and the Palace of Congress, where he made the speech.
Even government officials, who have publicly played down the importance of the latest guerrilla attacks, admitted they were tense and concerned the rebels might strike again during the parades, pomp and ceremony surrounding the speech.
The tension increased after the EPR rebels clashed with police and army units in two new incidents on Saturday in the southern state of Oaxaca and attacked an army commando in another state, Mihoacan. At least two people were killed.
While avoiding naming the EPR, Mr Zedillo raised his voice for the only time when he told congressmen: "We Mexicans cannot accept that just when the country is back on its feet, groups appear who are dedicated to terrorism and murder. We will respect individual and human rights but we will act with the full force of the state."
His tough stand against the guerrillas brought him several standing ovations.
Earlier, he had been interrupted twice by a silent protest by a left- wing congressman who walked in front of the podium and peeled off anti- government placards. Jarring somewhat with Mr Zedillo's pledge of greater openness, all television stations switched cameras to cut out the protester.
While Mr Zedillo's government and its US allies have billed the guerrillas as upstarts who pose no threat to Mexico's stability, it would be wrong to under-estimate the strength of disillusionment in Mexico with the slow pace of change.
The EPR is a blossoming of 30 years of activity by dozens of urban and rural leftist groups. The movement traces its origins back to the student uprisings of 1968, which were fuelled by the cost of staging the Olympic games that year.
A "dirty war" by the authorities led to a wave of "disappearances", forcing the leftists underground.
One such group, the Forces of National Liberation (FLN), joining with Mayan Indian peasant groups, metamorphosed into the Zapatista National Liberation Army (EZLN), which stunned Mexico with an uprising in Chiapas on New Year's Day 1994.
Typically, its members were mainly Indian peasants but its leaders, such as Subcomandante Marcos, the pipe-smoking intellectual in a black balaclava, were white or mestizo (mixed-race) intellectuals - disciples of the "class of '68".
Another group, the Party of the Poor (PDLP), continued to gather support in the southern state of Guerrero and linked up with a group in neighbouring Oaxaca called the Revolutionary Clandestine Workers' Party - Union of the People (Procup), to form the EPR.
The EPR first surfaced publicly on 28 June this year at Aguas Blancas, a village a short distance from the Pacific tourist resort of Acapulco, where guerrillas fired 17 rifle shots in the air to honour peasants killed in a massacre and gave a speech calling for the overthrow of the government.
Although the guerrillas were called a "pantomime", they abruptly cast off the label with the co-ordinated attacks in six states last week in which 15 people, mostly policemen or marines, were killed. The guerrillas then disappeared into mountain forests.Reuse content