Tomorrow Malcolm the office worker will kiss his wife and go to war

Malcolm Wells is an office worker, not a fighter, but he is going off to war nonetheless.

The 37-year-old oil company worker from St Albans has said goodbye to the boss and spent this weekend struggling up and down motorways to bid farewell to members of his family. Tomorrow he will kiss his wife, Jenny, pat their dog, Tia, and leave for the Gulf as part of the largest compulsory mobilisation of military reservists since the beginning of the Second World War.

The Ministry of Defence last week called up 3,500 men and women to augment the 1,500 already alerted for service in the Gulf. The Secretary of State for Defence, Geoff Hoon, says he may yet require another 3,000 to leave their civilian jobs, don combats and become soldiers, sailors and Air Force personnel "for the duration". If there is a conflict, they will be expected to play their full part.

Mr Wells started his working life as a scriptwriter for community theatre on Merseyside. He moved south to work in corporate communications, and got a job with the oil firm Sasol Chevron, which will now get financial compensation for his absence. He has been a Territorial Army officer for five years.

"Few employers these days carry surplus staff, so anyone going like this is bound to leave a hole behind," says his boss, Steve Colville, who is legally bound to keep his job open. "We are willing and happy for him to do this, but his colleagues will have to work harder while he is away. I knew he was in the TA when he joined us."

Reservists sign a contract of unlimited liability with their country, the sort of thing you would certainly refuse if an employer put it in front of you. But many of those who joined the weekend soldiers of the TA to indulge a sense of adventure, get fit, do their bit or just make new friends have been surprised and even alarmed to get buff envelopes calling them up to war. Serving alongside full-time fighters in a combat zone will be a huge culture shock to some.

"The Army has been good to me," says Mr Wells. "I've exercised in Virginia with the US Marines, and in Cyprus, and helped train others going to Bosnia." But this will be different: the bullets will not be blanks, casualties will not be simulated, and chemical warfare drills will have a horrible, added urgency.

He and Jenny were on holiday in Scotland when the attacks on Washington and the World Trade Centre took place. "We thought then that sooner or later I might be called up to play a part." Now he has put his life on hold. "I realise I'm not the only person affected by my decision, but I think it is the right thing to do and those around me agree."

Jenny looks down on a jumble of camouflage kit spread across the drawing room floor, and reflects that they have only been apart for two weeks in the past decade. "It will be a real trial for us," she says, but adds: "This is something he needs to do. Although I've had no previous experience of the military, I know that regular Army partners survive their other halves being away, and so will I."

The TA has 40,000 members, the majority of whom will not be going to the Gulf. But they may be called upon to provide cover at British bases and ports here and in Germany and Cyprus.

"I trust that the Army will use us well and send us home as soon as they can," says Mr Wells. "In return, the regular Army trusts the TA to really deliver its skills and numbers. I know we'll pass the test."

Paul Keetch, the Liberal Democrat defence spokesman, says calling up so many reservists emphasises the overstretch of the regular forces and places enormous pressure on volunteers and their families. However, Ministry of Defence officials insist they are not simply making up the numbers – this call-up is like buying in essential services, they say: logistics experts, medics and engineers who would not be needed in normal conditions, for example.

The MoD also claims to be practising "intelligent mobilisation" – mostly calling up those it knows are willing to go and have sympathetic employers. It does not expect many to contest their call-up.

Mr Wells is certainly not doing so, despite admitting his fears.

"Tying up the threads of your life and leaving everything in a neat and orderly fashion is the closest you'll ever come to seeing your own funeral," he says. "But I've been mentally packing for weeks now."

The historian Peter Caddick-Adams lectures at the National Defence Academy and is going to the Gulf with the Territorial Army