Answer: Tanks and military-grade planes
Explanation: Imperialism was about almost everywhere in Europe at the time and around that time most European countries had territories in Africa which lead to constant fighting for the land there. What this lead to was intense fights between nations by them creating proxy wars (militias/Rebel groups) to fight against each other which were being supplied by that country that wants more land for them self. With that it lead to Archduke assassination which lead countries to declare wars on one country which then would mean they would declare war on multiple countries in realty because countries would ally each other and the domino effect went down hill from that. So Archduke assassination was just really a "reason" to fight with another nation for more land (resources).
Prívate contacts keep everything as a secret without anyone knowing
Answer:
great Britain closed the port of boston
