David Cameron is evoking the risk of war in a warning about the dangers of leaving the European Union.
The Prime Minister will say peace in Europe cannot be guaranteed and it is in the UK's interest to be able to influence what happens to our neighbours.
But soon after Mr Cameron delivers a key speech marking an upturn in campaigning, Boris Johnson will deliver his own address making the "cosmopolitan case for Brexit".
He will then head out on a campaign battle bus tour across the country as both sides continue trying to persuade the public ahead of a 23 June referendum.
Mr Cameron will say: "For good or ill, we have written Europe's history just as Europe has helped to write ours."Play video "Top Tories Clash Over Single Market"Video:Top Tories Clash Over Single Market
"The moments of which we are rightly most proud in our national story include pivotal moments in European history. Blenheim. Trafalgar. Waterloo.
"Our country's heroism in the Great War. And most of all, our lone stand in 1940...
"The European Union has helped reconcile countries which were at each others' throats for decades.
"Britain has a fundamental national interest in maintaining common purpose in Europe to avoid future conflict between European countries.
"And that requires British leadership, and for Britain to remain a member. The truth is this: what happens in our neighbourhood matters to Britain.Play video "Leaving The EU: What Stays The Same"Video:Leaving The EU: What Stays The Same
"That was true in 1914, in 1940 and in 1989. Or, you could add 1588, 1704 and 1815. It is just as true in 2016.
"Either we influence Europe, or it influences us. And if things go wrong in Europe, let's not pretend we can be immune from the consequences."
Ahead of his speech, the Britain Stronger In Europe campaign group released a video featuring World War Two veterans calling on people to vote 'remain'.
Mr Cameron is expected to use WW2 leader Winston Churchill to boost his argument - even though the wartime PM has been used by the Leave campaign.
Mr Cameron will say: "In the post-war period he argued passionately for Western Europe to come together, to promote free trade, and to build institutions which would endure so that our continent would never again see such bloodshed."Play video "UK In EU: Key Issues From Campaigns"Video:UK In EU: Key Issues From Campaigns
His speech comes as the head of influential think tank Chatham House, Robin Niblett, says Brexit would lose the country influence and "weaken its sovereign power" outside the EU.
On Sunday, Brexit campaigner Michael Gove and pro-EU George Osborne traded blows over the prospect of Britain leaving the single market with Mr Gove saying it would increase the rate of growth and the Chancellor describing it as "catastrophic" for jobs and incomes.
A Vote Leave spokesman, responding to Mr Cameron's comments, said: "Claims that leaving the EU and taking back control would somehow lead to war smack of desperation from a campaign failing to make the case for the EU and our continued payment of £350m to Brussels every week.
"The PM's words are deeply ironic given the EU's own border agency says the EU's borderless policy is making the whole of Europe less safe. The safe option is to vote Leave."