The phrase "almost certainly attack" is correct and usable in written English.
It can be used when expressing a high degree of likelihood that an attack will occur, often in contexts related to security or military discussions.
Example: "Given the current tensions, the enemy will almost certainly attack our position by dawn."
Alternatives: "most likely attack" or "highly likely to attack".
Mr Assad would almost certainly attack such zones unless he were convinced that his own air defences and armour would be bombed.
The result would be that sooner or later he would almost certainly attack our planes, which would permit an escalating scale of reprisal and counter-reprisal that could permit us to deal conclusively with the problem of Castro.
Religious leaders and diplomats from Sierra Leone say that if the refugees return home, rebel soldiers and ordinary, desperately poor residents will almost certainly attack them and steal their new clothes, brand-name sneakers, even their prostheses.
Hillary Clinton will almost certainly attack Trump.
Talk of a skinny NAFTA that could be in the works has angered some congressional Democrats, who, if that comes to pass, will almost certainly attack Trump for being soft on trade, just as some did after the president's tweet defending ZTE.
But he said "there will almost certainly be attacks on the outside" of the Sochi security zone during the Olympics.
Connect an unprotected personal computer to the internet for more than 15 seconds and it will almost certainly be attacked by a virus or worse.
They said the Pentagon would almost certainly avoid attacks on chemical weapons depots because of the risk that poison gases would leak and disperse into the air.
Even so, when the sisters turned to Johns Hopkins, they found that a kidney donated by Mrs. Dick would almost certainly be attacked and destroyed by Mrs. Stahl's antibodies.
Others have almost certainly returned to attack the country which reared them.
ETA didn't officially claim responsibility for the killing (it usually waits weeks or months to do so), but it was almost certainly an ETA attack, the first successful one of the new year.
