A national day of commemoration in the UK and Belgium will mark 100 years since Britain's entry into the First World War, part of an epic four-year project to mark the centenary of the Great War.
With a build-up starting in June 1914, Britain declared war on Germany at 11pm on August 4, 1914.
As war raged over the next four years, millions of lives were lost in the devastating conflict, until the armistice was signed on November 11 1918.
A century on, the world is commemorating the Great War throughout the four-year period, with a series of major events next Monday marking Britain's entry into the war.
On August 4, s ervices of remembrance in London and Glasgow and a commemorative event in Belgium will be attended by members of the Royal Family and senior politicians from Britain, Ireland, Germany, Belgium, and the Commonwealth.
The Prince of Wales will attend a service at Glasgow Cathedral, which will be followed by a wreath-laying service and march-past at the Cenotaph in George Square.
Later that day, the Duke and Duchess of Cambridge and Prince Harry will attend an evening c ommemoration at the Commonwealth War Graves Commission's St Symphorien cemetery in Mons, Belgium, where the first and last British soldiers killed on the Western Front are now buried.
The event for around 500 invited guests will be narrated by historian Dan Snow and will include readings, music and poetry capturing the history of the site.
And at 10pm, a Service of Solemn Commemoration will be held at Westminster Abbey, attended by the Duchess of Cornwall.
It will include the gradual extinguishing of candles, with an oil lamp extinguished at the tomb of the unknown soldier at 11pm - the exact time Britain joined the war.
Anglican churches around the UK will hold similar services, including St Anne's Cathedral in Belfast and Llandaff Cathedral in Cardiff.
Acts of reflection will also take place in places of worship of other denominations and faiths, and Catholic churches will have held special Masses the day before.
And in the same hour, the nation has been urged to take part in Lights Out, which will see l ights switched off across the country in places of worship, public buildings, workplaces and private homes, with just one left burning in each place as a symbol of continuing hope in the darkness.
The project is a reference to then-foreign secretary Sir Edward Grey's famous remark on the eve of the outbreak of war, when he said: "The lamps are going out all over Europe; we shall not see them lit again in our life-time".
Next Monday's acts of commemoration are just part of a four-year project to mark the centenary of the Great War.
As part of a Government-backed programme to mark the centenary, ea ch of the 430 men awarded the Victoria Cross - the British Empire's highest medal for military valour - in the war will have their names enshrined in a paving stone in their home town.
Each stone will be installed on the 100th anniversary of the action for which the medal was issued, and will include a digital sign or QR (Quick Response) code giving people more information.
The first two, set to be laid in August, will commemorate Charles Garforth of Willesden Green in London and Sidney Godley of East Grinstead, and the scheme has also been extended to see foreign combatants who won the VC fighting for Britain during the war honoured.
The Government has contributed more than £50 million of funding to support commemoration activities, including an educational programme giving two students and a teacher from every state school in the country the chance to visit First World War battlefields and research local people who fought in the war.
Some £5 million, funded by Libor fines, will also be used to help conserve, repair and protect First World War memorials and graves across the UK and overseas.
There will also be a Christmas Day Truce football match on the battlefields of Flanders to mark the anniversary of the historic match between British and German soldiers on Christmas Day 1914, while the Premier League is donating a state-of-the-art floodlit football pitch in Ypres.
Culture Secretary Sajid Javid said: "A hundred years on, the sheer scale and sacrifice of the First World War demands remembrance.
"Breaking with tradition, we are marking the start as well as the end of the conflict so that the anniversaries of the war will improve our understanding of its causes, conduct and consequences."