The phrase "a direct operation" is correct and usable in written English.
It can be used in contexts where you are referring to an operation that is straightforward or without intermediaries, often in technical or procedural discussions.
Example: "The technician performed a direct operation on the machine to resolve the issue quickly."
Alternatives: "an immediate action" or "a straightforward procedure".
He added: "This was a direct operation to assassinate the leader of this country.
A direct operation playing a major part in current cryptography involves multiplying together two large numbers.
"This was a direct operation to assassinate the leader of this country," said the spokesman, Moussa Ibrahim.
The airstrikes on Saturday night killed a son and three grandchildren of Colonel Qaddafi, according to the government, which accused the NATO coalition powers of "a direct operation to assassinate the leader of this country" in violation of international law.
Not only did each of those companies go to market through different distribution channels, which meant exclusive agents, independent agents, and a direct operation, each company had their own products with various legal constructs, coverage, and coverage limitations.
In addition to the Mets, it also owns a book publishing company and a direct mail operation.
I think he finally left the business and set up a direct mail operation selling things like taps for shoes.
"If there was a direct military operation by the United States against Iran," one intelligence official said, "Mugniyah would likely attack us".
There are several irksome touches here – anyone who tweets #afterpartybook will apparently get their comment printed in an afterword to the paperback edition, which feels less like a brave literary experiment and more like a direct marketing operation.
He set up a "direct mail" operation, Rove + Company [sic], pinpointing potential Republican voters and sending them fundraising or voter registration letters written specifically to appeal to the target audience.
Interestingly, the agency I worked at soon started a Direct Marketing operation which I joined immediately after finishing my MBA.
