The Assassination of Wolfgang von Strucker was one of the opening actions in the Ultron Offensive.
During an assault on a HYDRA facility, Phil Coulson downloaded several files that revealed the location of Wolfgang von Strucker, who was using a Sokovian base to conduct illegal experiments with the Scepter Loki wielded during the Battle of New York.
Several days later, the Avengers launched a surprise attack on the compound and captured Strucker, who was later taken into custody by NATO. During the attack, Stark successfully recovered the Scepter, but not before Wanda Maximoff used her powers to implant a vision of the Chitauri invading Earth into his mind.
Deeply affected, Stark set out to complete the Ultron Program, a peacekeeping program designed to provide a proficient deterrent to any and all threats. The discovery of an artificial intelligence hidden within the scepter's gem prompted Stark and a reluctant Bruce Banner to configure a suitable A.I. structure for the program.
Upon completion, however, Ultron became unexpectedly self-aware and attacked the Avengers during a gala. Following the brief skirmish, he transferred his consciousness to the HYDRA compound and constructed an advanced body before recruiting Wanda and her twin brother Pietro to his cause.
After tracking down Strucker, Ultron forced him to reveal the location of several major Vibranium caches, which the artificial intelligence deemed necessary to carry out his plan to preserve peace.
Strucker provided Ultron with the location of Ulysses Klaue, a notorious gangster and black market arms dealer whose base of operations was a Salvage Yard located on the coast of Africa. A now-satisfied Ultron proceeded to smash Strucker's head against the wall of his cell, instantly killing the high-ranking HYDRA operative. Before escaping, Ultron took Strucker's blood and used it to paint the word "peace" across the wall, leaving it for the Avengers to find.
As Ultron and the Maximoffs traveled to Africa to meet with Klaue, the Avengers uncovered Ultron's message as well as Strucker's dealings with the master thief and followed Ultron to Africa.
Around the same time, HYDRA operative Gideon Malick seized the numerous vaults that were previously owned by Strucker, chief among them a vault in Zepkow, Germany that held a fragment of the Monolith.