。
The soldiers denied that they would obey that order.
Literal
Soldiers [topic-は] that order [target-に] obey [nominalizer-こと] [object-を] denied.
否定した (denied) is an unusual choice here — the more natural word would be 拒否した (refused). This reads like a somewhat stiff translation; 否定 implies denying a claim, not refusing an action. The nominalization ~ことを turns the verb phrase into a noun that can be the object of 否定する.