Subsequent activities and exile
Following his defeat, Osmeña continued as a leader in the Liberal Party. According to historian Joseph Scalice, Osmeña organized a covert organization called the Workshop Group, led by Terry Adevoso, that plotted to assassinate president Marcos in the early 1970s by hiring foreign contract killers. The hitmen's numerous attempts were thwarted, however, due to a mole in the organization named Jose Maristela that informed Marcos of their plans.
On August 21, 1971, Osmeña along with prominent members of the Liberal Party held a proclamation rally at the Plaza Miranda in Quiapo, Manila. While on stage with the other Liberal leaders, two hand grenades were thrown on stage, injuring Osmeña. The Plaza Miranda bombing injured 95, including Osmeña, and killed nine. Afterwards, Osmeña left for the United States and lived in Beverly Hills, Los Angeles, California.
Marcos proclaimed martial law in September 1972, citing the threat of the Communist Party of the Philippines and the rebellion of the Muslim Independence Movement. Marcos also submitted documents to the US Congress charging that the declaration of martial law was also due to a plot to kill him. He claimed that Osmeña was a key figure in the plot, although no formal charges were filed against him. Osmeña's son, Serge, was captured and imprisoned due to allegations that he was involved in the assassination attempts.
