The Deputy First Minister has raised concerns over the future of Scotland-based soldiers with the Defence Secretary.
In 2011 the UK Government said up to 7,000 personnel returning from Germany would be based in Scotland with a new barracks and training area built, but the SNP has warned that the number will be reduced.
Former Defence Secretary Liam Fox made the 2011 announcement to offset the closure of the RAF bases at Leuchars and Kinloss, but the SNP believes Phillip Hammond will not stick to the pledge when the UK basing plan is unveiled this week.
Nicola Sturgeon has written to Mr Hammond asking for clarification on the issue.
The Deputy First Minister said: "Scotland has already been disproportionately affected by the defence cuts, and despite suggestions that there would be an increase of between 5,000 and 7,500 in the number of Army personnel based here, we now hear those commitments will not be met and that any increase may be limited to only a few hundred army personnel.
"That will do little to halt the long-term and disproportionate decline in the overall numbers of military personnel in Scotland."
In her letter, Ms Sturgeon said the uncertainty is adding to the "anxiety" for the service personnel and their families who will be affected.
Ms Sturgeon wrote: "Where our communities are given the chance they demonstrate time and again that they extend an excellent welcome to the military personnel who live amongst them, as we have most recently seen with the very positive move of 39 (Engineer) Regiment to Kinloss.
I therefore want to take this opportunity to urge you once again to reverse the long-term and disproportionate decline in the military footprint that Scotland has seen over the last decade and, crucially, to meet the commitments that were made by the UK Government in July 2011."
The Ministry of Defence has yet to comment on the claims.