Franco-Prussian War
Ems Dispatch -- Otto von Bismarck by re-editing a telegram from the Prussian King so that it appeared as though the King had insulted a French ambassador during a time of extremely tense French-German international relations. The telegram is known as the Ems Dispatch. It helped encourage the states to go to war.
World War II
One of the most notable examples was in World War II when the German commerce raider Kormoran, disguised as a Dutch merchant ship, surprised and sank the Australian light cruiser HMASSydney in 1941, causing the greatest recorded loss of life on an Australian warship. The Kormoran was also fatally crippled in that encounter and its crew was captured, but it was a considerable psychological victory for the Germans.
Reichstag Fire
The Reichstag fire was an arson attack on the Reichstag building in Berlin on 27 February 1933. The fire started in the Session Chamber, and, by the time the police and firemen arrived, the main Chamber of Deputies was engulfed in flames. Police searched the building and found Marinus van der Lubbe, a young, Dutch council communist and unemployed bricklayer who had recently arrived in Germany, ostensibly to carry out political activities.
Winter War
In 1939 the Red Army shelled Mainila, a Russian town near the Finnish border. Soviet authorities blamed Finland for the attack and used the incident as a pretext to start the Winter War four days later.
Operation Ajax
The replacement of Iran's Anglo-Persian Oil Company with five American oil companies and the 1953 Iranian coup d'état was the consequence of the U.S. and British-orchestrated false flag operation, Operation Ajax. Operation Ajax used political intrigue, propaganda, and agreements with Qashqai tribal leaders to depose the democratically elected leader of Iran, Mohammed Mosaddeq. Information regarding the CIA-sponsored coup d'etat has been largely declassified and is available in the CIA archives.
and our favorite...
Gulf of Tonkin incident
The Gulf of Tonkin incident (or the USS Maddox incident) is the name given to two separate confrontations involving North Vietnam and the United States in the waters of the Gulf of Tonkin. The first event occurred on August 2, 1964, between the destroyer USS Maddox and three North Vietnamese Navy torpedo boats of the 135th Torpedo Squadron.[23] The second was originally claimed by the U.S. National Security Agency to have occurred on August 4, 1964, as another sea battle, but instead may have involved "Tonkin Ghosts"[24] (false radar images) and not actual NVN torpedo boat attacks.
The outcome of these two incidents was the passage by Congress of the Gulf of Tonkin Resolution, which granted President Lyndon B. Johnson the authority to assist any Southeast Asian country whose government was considered to be jeopardized by "communist aggression." The resolution served as Johnson's legal justification for deploying U.S. conventional forces and the commencement of open warfare against North Vietnam.
of course these events are just figimint of the imagination of "fringe conspiracy theorists" who know how to look up historical events... I am sure nothing like this will happen in future...