Government lawyers have asked a High Court judge to block families' attempts to claim compensation for British soldiers killed in Iraq.
Relatives of four soldiers killed in separate incidents say the Ministry of Defence failed to provide armoured vehicles or equipment which could have saved lives.
But the MoD said the claims should be "struck out" because such vehicles and equipment were not available when the soldiers died, and argued that "complex" decisions about military equipment should be left to politicians and commanders not judges.
Lawyers said the hearing in London would last three days, although judge Mr Justice Owen is expected to reserve judgment.
James Eadie QC, for the MoD, told the court the compensation claims related to an incident in which a British Challenger tank opened fire on another British Challenger tank, after an officer became "disorientated", and incidents in which soldiers died when Snatch Land Rovers hit improvised bombs.
Corporal Stephen Allbutt, 35, of Sneyd Green, Stoke-on-Trent, Staffordshire, died from "friendly fire" in March 2003 after his Challenger 2 tank was hit by another Challenger 2 tank.
Private Phillip Hewett, 21, of Tamworth, Staffordshire, died in July 2005 after a Snatch Land Rover was blown up. Private Lee Ellis, 23, of Wythenshawe, Greater Manchester, died after a similar incident in February 2006 and Lance Corporal Kirk Redpath, 22, of Romford, Essex, died following a similar explosion in August 2007.
Mr Eadie told the court that families were alleging that the two tanks involved in the "friendly fire" incident should have been fitted with "tactical safety equipment" - "target identity" or "situation awareness" devices.
He said at the time the UK was looking to procure "battlefield identification systems" but the programme was in a developmental stage and not available.
Mr Eadie said families were also alleging that soldiers killed in Snatch Land Rovers should have been travelling in vehicles with tougher armour.