Hiring mercenaries has had both direct and indirect economic implications. Directly, mercenaries demanded high wages, and states had to allocate substantial resources to finance them. This could strain the national treasury, especially during prolonged conflicts. Indirectly, employing mercenaries could lead to economic benefits. For instance, by avoiding significant citizen casualties, nations could maintain a productive workforce, which is essential for a thriving economy. Moreover, with mercenaries handling some of the warfare, states could divert their native populace towards activities like agriculture, trade, and manufacturing, boosting economic output.

Colonial powers often had mixed approaches to mercenary practices in their colonies. In some instances, they actively employed mercenaries, or "private military companies", to maintain control, suppress local uprisings, or wage proxy wars without directly involving their national armies. This allowed them to maintain a facade of neutrality or minimal involvement. In other situations, colonial powers suppressed mercenary activities, especially if they threatened the stability of their rule or if the mercenaries sided with anti-colonial movements. The economic and strategic interests of the colonial power largely dictated their stance on mercenaries.

Switching allegiances was a risk associated with hiring mercenaries. One renowned group is the Varangian Guard. Originally Viking mercenaries, they became the elite guard of Byzantine emperors. However, their loyalty, especially during political turmoil, wasn't always guaranteed. In various instances throughout history, mercenaries changed sides, lured by better pay or more favorable terms. Such shifts could have dire consequences for the hiring state, including unexpected defeats in battles, leaks of critical military information, or even the overthrow of ruling elites. This unpredictable nature of mercenaries made states cautious and underscored the need for robust, loyal national armies.

Offensive alliances have been less common than defensive ones but have still played crucial roles in history. One such example is the Pact of Steel between Nazi Germany and Fascist Italy in 1939, which aimed at mutual support against France and the UK. This alliance later expanded to include Japan, forming the Axis Powers during World War II. The implications were profound: these aggressive partnerships led to coordinated attacks on multiple fronts, adding complexity to war strategies and necessitating the formation of counter-alliances like the Allies. These alliances significantly influenced the scale, duration, and strategies employed in the global conflict.

Yes, throughout history, states have tried to devise diplomatic solutions to avoid the pitfalls of alliances. One notable effort was the Concert of Europe, initiated after the Napoleonic Wars during the Congress of Vienna in 1815. This was a system where the major European powers - Britain, Russia, Prussia, Austria, and later France - would meet periodically to resolve their disputes diplomatically, thus averting large-scale wars. Another example is the Kellogg-Briand Pact of 1928, where nations committed to resolving disputes peacefully. While these efforts were noble, they often proved insufficient in preventing conflicts, as was evident with the outbreak of World War II.