Former British Prime Minister Tony Blair should take responsibility for sending his country to war in Iraq. Blair was a major supporter of the war; arguing that it was necessary to remove Saddam Hussein from power. The Iraq War killed thousands of American, British, Allied troops, as well as thousands of civilians. Furthermore, it led to a destabilized Middle East which gave rise to ISIS. In short, Tony Blair should take responsibility for the terrible outcome of taking Great Britain to war.
Although I feel that the responsibility lies with more than one person, ultimately the former Prime Minister is responsible in the same way that the United States President was also responsible and should be held accountable for the cost to his government and people. The blow-back from the war has created larger terrorist groups, and fueled deeper mistrust and hatred for Britain at the cost of many innocent lives.
It was ultimately Tony Blair's decision to go to war with Iraq, so he absolutely should take responsibility for it. The deaths and aftermath are directly his fault, no matter what the research said beforehand and investigations say afterwards, it was his choice. Blindly following the US was a terrible decision that he is responsible for.
Yes, Tony Blair should accept some responsibility for sending Britain to war. Both Blair in the U.K. and George W. Bush in the U.S. hold degrees of culpability for starting the Iraq war, which resulted in the lawless environment that bred the rise of ISIS and terrorism around the world.