South Africa's President Jacob Zuma has ordered the deployment of about 440 troops to maintain law and order in parliament for his annual state of the nation address on Thursday.
Opposition parties have condemned the decision as a "declaration of war".
Previous addresses by Mr Zuma have been marred by protests and brawls as opposition MPs demanded his resignation.
Mr Zuma has been dogged by corruption allegations for more than a decade.
A statement from the president's office released on Tuesday said Mr Zuma had authorised the deployment of soldiers to work with the police.
It is the first time that troops will have a security rather than a ceremonial role.
According to reports quoted in a local media, intelligence sources have warned there could be massive uprisings at Thursday's event. Their alerts prompted fears that the police would not be able to cope on their own.
Past state of the nation speeches have been marred by chaos in parliament.
Since winning seats in 2014, members of the Economic Freedom Fighters' party (EFF) have caused disruption by chanting and jeering at the president over allegations of corruption.
In 2015, EFF members were removed from the chamber by security guards disguised as waiters.
But the main opposition Democratic Alliance (DA) has condemned the president's decision, describing the move as "deeply concerning".
"President Zuma's deliberate use of the words 'law and order' in his statement points to an excessive use of the army outside of their ceremonial role in the annual fanfare," a statement for the DA said.
'No confidence' in the president - Milton Nkosi, BBC News, Johannesburg
Hundreds of people from South African civil rights groups have gathered in Cape Town's St George's Cathedral under the Save South Africa campaign, in what they call the "real State of The Nation" ahead of President Jacob Zuma's address on Thursday.
Many speakers took to the podium to condemn President Zuma's style of leadership.
The campaign's leader Sipho Pityana, an anti-apartheid activist and an African National Congress member, told the meeting that the speaker of parliament must not address President Zuma as "honourable".
He said of Mr Zuma: "You must know that as a nation we no longer have confidence in you as a president."
"You have used every opportunity to bring shame to a glorious movement, the African National Congress," he said.
'Trained to kill'
The EFF called the announcement a "declaration of war" on the country's citizens.
"The military are people who get deployed for war and whose training is about killing the enemies of the state," spokesperson Mbuyiseni Ndlozi said.
The party has continually denounced Mr Zuma as an "illegitimate" ruler who should step down.
Jacob Zuma: Key facts
- With no formal schooling, he joined the ANC at 17 and was jailed for 10 years on Robben Island alongside Nelson Mandela
- A charismatic politician, he shook off various scandals to become president in 2009
- But his presidency has been dogged by allegations of corruption
- Last year, the Constitutional Court ruled he had breached the constitution by failing to repay government money spent on upgrades including a swimming pool and chicken run at his private home in Nkandla
- The anti-corruption watchdog then said a judicial inquiry should be set up to further investigate allegations of criminal activity in government in relation to the Guptas, a business family with links to Mr Zuma
- The 74-year-old survived three no-confidences votes last year, two in parliament and one within the ANC
- He is due to step down as ANC leader in December and as president after general elections in 2019.
There have been accusations of undue influence on the government by a wealthy Indian-born business family and of violations of the constitution.
An investigation carried out last year by the former public protector of South Africa found evidence of possible corruption at the top level of government.
The country's highest court ruled last March that President Zuma had violated the constitution when he failed to repay government money spent on his private home in Nkandla.
Mr Zuma has repeatedly denied any malpractice.
His presidential term is due to end in 2019.
But the governing African National Congress (ANC) is due to elect a new leader in December, at which point he may come under increased pressure to also step down as national leader.