Sir Richard is seen as an outspoken defender of the Army's interests
The head of the Army has said UK armed forces risk becoming "increasingly irrelevant" if the Ministry of Defence does not "adapt across the board".
Gen Sir Richard Dannatt said there remained a "Cold War mentality", geared to combating threats from other states.
But troops were now more involved in counter-insurgency operations, he said.
He told the Chatham House think tank that the fight against al-Qaeda and other militant Islamist groups was "probably the fight of our generation".
Sir Richard warned that British forces could expect to be involved in combating "predatory non-state actors" for the foreseeable future, in what he called an "era of persistent conflict".
BBC diplomatic correspondent Paul Adams says Sir Richard "clearly does not believe the UK's armed forces are properly organised or equipped for such sustained efforts".
The general said that only 10% of the MoD's equipment programme between 2003 and 2018 was to be invested in the "land environment" - at a time when Britain was engaged in two land-based military operations.
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