To answer that question, one would need to determine how the spending is allocated—what these amounts would be spent on. For example, if it was to increase the number of Canadian Forces members or even civilian personnel, that would create wage pressures. There would not be tremendous wage pressures, but it would contribute to labour shortages. However, if it was to acquire goods or military equipment produced abroad, it would add very little inflationary pressure.
The magnitude of the inflationary pressures created would depend on the type of spending made with this $18 billion. If it's all on personnel, it will exacerbate or put additional pressure on inflation. It would be the same if it went to purchasing domestically produced goods.