National and military authorities were reluctant to adopt the weapon, and Maxim's company initially had some trouble convincing European governments of the weapon's efficiency. Soldiers generally held a great mistrust of machine guns due to their tendency to jam. In the 1906 version of his book "Small Wars", Charles Callwell says of machine guns: "The older forms are not suitable as a rule... they jammed at Ulundi, they jammed at Dogali, they jammed at Abu Klea and Tofrek, in some cases with unfortunate results." However, the Maxim was far more reliable than its contemporaries. A more immediate problem was that, initially, its position was easily given away by the clouds of smoke that the gun produced (although the same was true of artillery pieces and units of troops that the machine gun was intended to replace or supplement, so this wasn't viewed as a particular drawback by the early users). The advent of smokeless powder (developed by, among others, Hiram's brother Hudson Maxim), helped to change this.