"France did not want peace to be negotiated," after Gbagbo refused to accept that Ouattara had won the poll and holed up in the presidential palace, defence lawyer Emmanuel Altit told the court on the third day of the trial.
"Ouattara and his supporters wanted to seize power by force and the battle of Abidjan was, simply put, the very implementation of this strategy," he said, referring to post-election conflict that left some 3,000 people from both camps dead.
Gbagbo, 70, is the first ex-head of state to go on trial at the ICC and proceedings are expected to last three to four years.
On Thursday chief prosecutor Fatou Bensouda accused Gbagbo of clinging onto power "by any means necessary", with the help of the military, the police and a youth militia led by Blé Goudé, 44.
The prosecution is concentrating on four events in its case against Gbagbo and Blé Goudé, including the shelling of a market that killed 40 people and injured 60.
But Altit insisted there had been a "smear campaign" against his client and accused pro-Outtara forces of abuses.
When Gbagbo declared himself the winner, France, the US and the UN backed Ouattara.
Then French president Nicolas Sarkozy "had shown unwavering support for his friend Ouattara," defence lawyer Jennifer Naouri told the court.
"The plans for military action had been drawn up by the plotters and schemers ... in cooperation with French military leaders during the entire crisis," Altit said. "A fleet of French military aircraft delivered heavy weapons to pro-Ouattara combatants in the north of Cote d'Ivoire in February and March 2011, once again breaking the UN embargo."
The UN's condemnation of the market shelling led to "a ground offensive which had been prepared well in advance, craftily, sneakily, by French forces," he said, asking why the prosecution had called no French witnesses, who were the only people to have information that would establish the truth of what happened.
The ICC is accused by some African leaders of unfairly targeting them.
On Sunday, during an African Union summit, several heads of state backed a Kenyan proposal to pull out of the ICC on the ground that it is biased.