A Royal Marine from County Antrim made 14 pipe bombs which were to be used by dissident republicans to attack police.
A court hearing to decide how long Ciarán Maxwell will serve in prison is taking place at the Old Bailey.
The court heard that four of the pipe bombs were used in Northern Ireland - and two detonated.
In February, Maxwell, 31, admitted a number of offences, including bomb-making and storing stolen military weapons.
The Larne man also pleaded guilty to drugs and fraud charges. The sentencing hearing is expected to take up to three days.
Maxwell is not in court, but is appearing via video link from Woodhill Prison in Milton Keynes.
According to the charge details, he had a stash of explosives in 12 purpose-built hides in England and Northern Ireland.
DNA evidence found at one of the County Antrim hides led to Maxwell's arrest.
'Our day will come'
On Wednesday, the court heard that documents found on a memory card of Maxwell's included a Mujahideen explosives handbook and the IRA's Green Book - or rule book.
It also contained images of Larne police station marked manually with a blast radius graphic.
The card had maps, plans and lists of potential targets, as well as images of an adapted PSNI pass card and items of PSNI uniform, addresses of police officers, names of military staff, details of an MI5 member and of loyalists.
Maxwell also bought chemicals and components and went on to manufacture explosives.
His wi-fi password was "tiocfaidh1" - a derivation of the Irish republican phrase "tiocfaidh ar la", or "our day will come".
Maxwell told police he had taken a member of the Continuity IRA to a hide where he had stashed pipe bombs in Northern Ireland.
The court was told the man he took to the hide was Niall Lehd, convicted in 2014 of possession of an explosive substance with intent to endanger life.
Maxwell had handwritten "to-do lists" mentioning "targets, dummy runs and recces" and a number of towns in Northern Ireland.
The exact details were redacted by the court, but the targets included a Territorial Army centre and Ballylumford Power Station.
There was also reference to a loyalist group, the need to notify news agencies, while under the heading "Easter leave tasks" were the words "test pipe bomb and car bomb".
In one of his hides, Maxwell placed a modified booby-trapped torch which, when armed, would explode if turned on.
Maxwell lived in Exminster in Devon, and was based with 40 Commando in Taunton, Somerset. He never served in Northern Ireland.
He was arrested last August and a search near Exeter found hides with a range of explosive substances, as well as ammunition, weapons and tools for making bombs.
Along with the 14 pipe bombs, the court heard Maxwell also stashed:
- Two anti-personnel directional mines
- Two explosively formed projectiles (EFPs)
- 29 complete explosive firing systems
- 33 initiators (part of a detonator for explosives), including two military initiators
- 13 military "igniter safety fuze electric" initiators
- Three fully-constructed improvised detonators
- Other component parts for IEDs [improvised explosive devices]
- Other materials and chemicals to make explosives
- A replica handgun and ammunition
On Wednesday, prosecutor Richard Whittam QC told the court: "Across 14 of the locations involved in the investigation, Mr Maxwell had in his possession, or had constructed, 14 pipe bombs... four have been deployed in Northern Ireland.
"It is our case that some of the items inevitably must have been taken from the UK to Northern Ireland by this defendant."
He added: "It may be that, when travelling between England and the UK, bearing in mind the identity cards he would have had, and his position, his passage would have been easier than others to take items with him."
The court heard dissident republicans have carried out more than 160 terrorist attacks since 2010, including the deployment of improvised explosive devices (IEDs) such as pipe bombs.
Mr Whittam said: "Whilst attacks are mainly directed at members of the police, military and prison service, the nature of the attacks leaves members of the public at risk."
The court heard that Maxwell "appeared shocked" when he was arrested.
During interview he told police he "got in over his head and didn't know how to get away". He was interviewed 22 times, remaining silent during the first seven.
After his arrest, drugs were found in locker at the camp, including herbal cannabis, cannabis resin, and hallucinogenic drugs DMT and LSD.
The Old Bailey was told that of the four pipe bombs constructed by Maxwell were used in Northern Ireland in the past year - in Belfast, Armagh and Carnlough. Only the device in Armagh detonated.
Another pipe bomb made by Maxwell exploded in Larne in 2013.
Two of the pipe bombs were used before Maxwell was arrested, and two after.
In March 2016, police said bomb-making parts had been found in barrels hidden in a wooded area in Carnfunnock County Park in County Antrim.
Two months later, another "terrorist hide" was found in Capanagh Forest, also near Larne.
Police described it as one of the most significant arms finds in recent years.
Of the pipe bombs found at Capanagh, Wednesday's hearing was told: "The grooves in the pipe bombs would aid fragmentation increasing the potential for the devices to cause injury.
"Depending on the amount of explosive used, the devices could cause serious injury and possibly death to anyone in close proximity at the time of detonation."
Of particular concern to security chiefs was the discovery of military grade anti-personnel mines.
Parts for making explosive devices also made up part of the haul.
Their serial numbers revealed they had been taken from the Royal Marines base in Somerset where Maxwell was based.