The Parsons Green bomber has told jurors he was never taken prisoner by Islamic State and had not had any contact with the terror group.
Iraqi asylum seeker Ahmed Hassan arrived in Britain in October 2015 and went on to tell immigration officials he had been forced to train "to kill" by IS, the Old Bailey has heard.
Then on September 15 last year, the 18-year-old media student planted 400g of homemade explosives and shrapnel on a District line Tube timed to go off when it reached the west London stop, the court has heard.
When he was picked up at the port of Dover the following morning, he told police he had made the bomb, which only partially exploded on the packed rush hour service.
Giving evidence in his defence, Hassan told how he was born in Baghdad.
His mother died when he was young and his taxi driver father was killed in an explosion in 2006, he said.
"So far as I'm aware, I was told that he died in an explosion while he was working as a taxi driver. He used to go to work and come back evenings and then he did not come back.
"It was very difficult. I did not understand what was going on. I was in a state of confusion because of fighting, because of bombing."
Hassan told jurors he moved to northern Iraq with his uncle and older brother, and from the age of 12 worked ferrying goods such as vegetables across the border with Iran.
The defendant said he decided to leave Iraq because he wanted "a better life".
He said: "I wanted studying, I wanted to learn English and there was so much pressure on me to keep on with my job."
He smuggled himself to Britain by train and on a lorry at the age of 16, he said.
Hassan, who was living with foster parents in Sunbury, Surrey, has denied attempted murder and using the chemical compound TATP to cause an explosion that was likely to endanger life.
The teenager told jurors he made up a story about being kidnapped by IS to get leave to remain in Britain.
Asked why, he said: "Because I came from a wealthy, safe area in northern Iraq in Kurdistan and if I told the truth, my only reason to leave the country was to further my studies ... I felt I had to make up something strong.
"In the jungle in Calais, people used to talk about these things and make up stories. I never came across a refugee who said he would tell the truth when he arrived in the country."