Polnay said analysis of Bashir and Al-Shamie’s WhatsApp messages to each other “demonstrated they were both close associates and both shared in an extremist world view”.
“They were both interested in, and regularly discussed, violent jihad.”
The prosecution said some of these WhatsApp exchanges were about “getting ready for ‘war'”.
Polnay said: “CCTV from the Sunnah Mosque in Manchester, combined with [data from a phone belonging to Al-Shamie], demonstrates that both men were planning a terrorist attack on the [defence] Station at Shrivenham in advance of 14 August.”
CCTV images played to the court showed what the two men were looking at on the screens of their mobile phones, five days before the trip to Shrivenham.
The footage also recorded the sound of their conversation.
Al-Shamie accessed the Defence Academy UK website and also looked at a websites with articles about UK links to the Israel-Gaza war, the court heard.
The CCTV played to the court also showed Bashir making a gesture with the raised index finger of his right hand. The prosecution said this gesture was associated with jihadist groups.
Melvin Cravitz and Adrian Daulby were killed after 35-year-old Al-Shamie, from Prestwich, drove his Kia Picanto into the gates of the synagogue and began attacking people with a knife.
Al Shamie, who was wearing a fake suicide belt, was killed by police gunfire at the scene.
Bashir went to Pakistan following the synagogue attack, but was arrested at Manchester Airport when he returned.
The sentencing hearing is expected to last two days.