In the event of a Yes vote in next year's referendum, Scotland has a variety of options in developing its own defence forces.

The obvious first option would be to create a Scottish Defence Force based on what can be transferred from the departing UK armed forces.

Another option would be based on the Irish model. The lessons from the Irish experience are both positive and negative. The Irish spend only 0.6 % of GDP on defence, the joint lowest in the EU. This is way too low.

Scotland should not follow the Irish in this but could aim at a spending level of 1% to 1.2%, similar to Belgium. This would still be substantially lower than the UK at 2.6%, France (2.2%), Denmark (1.4%) and the other EU neutrals, Sweden (1.3%) and Finland (1.5%).

However, prolonged exposure to underinvestment has resulted in the Irish Defence Forces (IDF) becoming exceptionally efficient in maximising the funding available. It has produced versatile forces that are very much "fit for purpose", tailored to carry out the roles laid down by Government.

A feature of the Irish system is the devolution of budgets to the military. This has allowed for more accurate financial decision-making, as the military is best placed to assess the cost-effectiveness of programmes. In comparison with other EU forces there is a higher emphasis in Ireland on participation in international peacekeeping operations than in national defence. This could also be true for the SDF.

The IDF has contributed to UN, EU and Nato missions with an overall self-imposed ceiling of 850 personnel abroad at any one time, which is approximately 10% of the Army.

It is important to have such a target ceiling, otherwise the forces and personnel will suffer. Ireland has avoided overextending its resources overseas, in part out of consideration for family life.With an older age profile than most armies, due to a higher percentage of re-enlistments, the majority of Irish personnel serving overseas are married or in long-term relationships. As troops are older and very experienced, over half of personnel have completed multiple tours of overseas service.

Based on the Irish model, I would recommend that an independent Scotland would consider having a ceiling in the region of 1100 SDF personnel, to include a mechanised battalion and other combat service support army elements, similar to Ireland.

However, I would further recommend that the Scottish Navy has a capacity to contribute to an international peacekeeping mission, perhaps, for example, a warship for anti-piracy operations. In the case of a Scottish Air Force, troop-carrying helicopters would be a useful asset, as would a logistics aircraft, such as the C130 Hercules, left. The enlistment terms for Irish personnel include agreement to participate in overseas missions.

The Scots, however, should not follow the Irish "triple lock" requirement. For Irish forces to participate in an overseas mission, there has to be a Government decision, parliamentary approval and – crucially – UN approval. The last of these means that the veto of a permanent member of the UN Security Council could block participation in a mission that is in Scotland's interests.

The IDF has always had to compete with its UK counterpart for recruits. That it has done so, quite successfully, should give encouragement to the Scots. The SDF will need to be an attractive career option. Planners for the new SDF should look at the Irish model, where personnel have representative bodies, and where there is a Defence Forces Ombudsman.

In Ireland, the serviceman and servicewoman are citizens of the state, not subjects of the monarch. This means they have the full rights of a citizen before the courts.

A very strong card to play would be to follow the Irish example of the soldier being an integral part of his community. While enlisted personnel can be transferred, in practice soldiers can remain their entire career, if they wish, in or near their home town. This means they put down roots and become part of the community. Once their recruit training is finished, they are given permission to live outside barracks.

With regards organisation, I would like to recommend a different Army structure than currently envisaged. Instead of a Regular Army Brigade and a Territorial (Reserve) Army Brigade, I would suggest two operational brigades, with regular and reserve personnel integrated at unit level, similar to the current Irish model. This would allow for six battalions, possibly four mechanised infantry battalions, one armoured battalion and one mountain-warfare battalion. Each brigade would have a light-artillery regiment, a reconnaissance squadron, a field-engineer company and combat-service support units.

The ratio of regulars to reservists would be approximately three to one. The integration of regulars and reservists would maximise use of common resources. The army should have a geographical spread with perhaps seven to eight battalion-sized posts, plus a training centre and a logistics centre.

Two operational brigade HQs will make tasking much easier and, with six battalions, it will allow greater flexibility to facilitate overseas rotations and home training.

At Army level there should be a Special Forces unit, possibly similar to the Irish Army Ranger Wing, and an air-defence unit. The Scottish Navy should also have a marine infantry component, which the Irish do not have.

These are just a few of the lessons from considering the Irish model. Hopefully, they will get SDF planners thinking.