Gaps between soldiers' tours are being extended by six months as the "relentless" pace of operations takes a toll on their marriages, the head of the Army said.
General Sir Richard Dannatt said servicemen and women had been "seriously stretched" by years of fighting in Iraq and Afghanistan, and would see time between overseas deployments rise to 30 months from two years as a result.
The Army was also "undermanned" and needs to be larger, he added, in what are being seen as his most outspoken comments yet.
In a speech to the Institute for Public Policy Research in London, Gen Dannatt said: "Many families and marriages have unfortunately fallen victim to the relentless pace of operations.
"We have seriously stretched our soldiers - both their goodwill and their families."
The general, who retires as Chief of the General Staff later this year, said he was reforming the Army's fighting brigades into larger units that can be sent away less often. This will see the ten brigades currently comprising around 4,000 men streamlined into six.
Gen Dannatt said: "A gap of one year between operational deployment is not unusual and often soldiers are spending much of the year before a deployment away from home, in training and preparation. This is unacceptable.
"The Army should be about 102,000 soldiers. It is currently about 98,500. By definition we are undermanned.
"There is a very strong argument for the size of our land forces to be larger."
He also criticised delays announced by the Government for the Army's next generation of armoured vehicles, saying much of what soldiers travelled in "harks back to the Sixties and Seventies".
