A Muslim convert dubbed Jihadi Jack was sent money by his parents while in Syria, despite evidence he was a member of Isis.
Farmer John Letts, 58, and his wife Sally Lane, 56, are on trial accused of sending or trying to send sums totalling £1,723 to their son.
Jack Letts left the family home in Oxford in 2014 aged 18, the Old Bailey heard.
The court heard how his mother, a former fundraising and marketing officer, had bought him a flight to Jordan, despite warnings that he planned to go and fight in Syria.
He then travelled to Kuwait and then on to Iraq and Syria, the jury was told.
On October 1 2014, Lane told one of her son’s friends he was ‘OK for now’ but ‘in the worst place possible and doesn’t want to leave’.
The next day, Letts revealed to a friend that he was in an ‘Isis area’ but not fighting.
The friend allegedly said: ‘It sounds like he’s having the adventure of a lifetime.’
By early 2015, the defendants knew their son had married in Iraq and had no intention of returning to Britain, jurors heard.
Mr Letts accused his son of lying about his plans to leave and said he was a ‘pawn… helping to spread hatred, pain, anger, suffering and violence’.
In March 2015, police visited the defendants and formally warned them they risked prosecution if they sent their son property or money, jurors were told.
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When he found out about the raid, Jack Letts allegedly responded: ‘Please convey to the British police that I’m not planning on coming back to their broken country.
‘Convey to them from me ‘Die in your rage soon you’ll be the ones being raided!’
In May, he posted a picture of himself standing on the Taqba Dam in Raqqa, the heartland of IS territory, jurors were told.
In July 2015, a former school friend called Linus Doubtfire, posed a picture to Facebook with a group of British Army colleagues after completing his Commando Artillery Course.
Letts commented: ‘I would love to perform a martyrdom operation in this scene.’
Prosecutor Alison Morgan QC told how the defendants appeared shocked by his Facebook post.
Lane allegedly urged her son not to be ‘so stupid’, saying: ‘How did we bring you up to be so easily manipulated?’
He responded: ‘I admit it was wrong if I seemed like I was joking. I genuinely believe attacking the British Army is a very praiseworthy action when the intention is correct.
‘I would happily kill each and every one of Linus Unit personally.
‘This message for you, Mum and (younger brother) Tyler, I honestly want to cut Linus head off.
‘I hope he finds himself lost in Beji or Fallujah one day and sees me whilst I’m armed and I put six bullets in his head.’
His mother replied: ‘I’m really hoping that your disgusting comments about cutting people’s heads off are not coming from you, i.e. someone else is using your account.’
Ms Morgan said the significance of the exchange was that the defendants were never sure they were communicating directly with their son, let alone that the transfers they went on to make would go to him or what the money would be used for.
The couple, of Chilswell Road, Oxford, have denied three charges of funding terrorism.