A useful article. I think one interesting example is the involvement of US troops in the First World War and how long this took to organise. Despite the US obsession with guns it had a small army and one which had not performed well in the Punitive Expedition to Mexico 1916/17 despite which the commander of that, Pershing, was made commander of the American troops sent to France. It was not simply a question of soldiers. National Guard units were quickly transformed into regular regiments, but also of equipment. We probably all know that some US troops went into battle in uniforms dating back to the American Civil War. Much of the equipment and uniforms supplied to the AEF in the early months came from the French. The lack of expertise Salt mentions was clearly shown in France with the casualty rates for the Americans seven times higher than equivalent British and French soldiers. Not only were many of the Americans 'green' they had not had 3+ years experience in trench warfare; they were like the British and French forces of 1914.
There were factors that worsened the situation for the AEF. First the Americans were associates, not allies of the British and French and Pershing insisted on their own stretch of the front, when it would have been safer to mix in newly arrived American units alongside British and French (and indeed Belgian and Portuguese) ones. Conscription 'by number' meant that the US forces had men of different races but they were not permitted to serve side-by-side in the US Army until 1948. Thus, four black regiments (369th, 370th, 371st, and 372nd) were given to the French, welcome of the manpower. These regiments benefited from that inter-mixing with hardened veterans that the white units lacked. Those kept by the AEF were not seen as suited to frontline combat and were assigned support roles the way that the British used Chinese labourers in their sectors. Despite all these disadvantages the AEF was important in defending Paris during the Second Battle of the Marne, June-August 1918.
I just highlight this example to bring out the fact that in addition to the challenges that Salt shows, even once you have begun assembling your larger army, it takes time to be effective and it getting beyond the high casualties of 'green' units can be aided or hindered by the approaches adopted for that larger army. If Pershing had not been so dogmatic about standing alone, he could have reduced the casualties of his units. As for the US Army dealing with its racial approach, that was a problem that US society struggled to grapple throughout the rest of the 20th Century and indeed beyond. Thus, difficulties can arise not simply among the units a commander controls, but the context from which those units are drawn, which again can impact on the effective use of the soldiers.