10 Changes Star Trek Hoped You Wouldn't Notice
3. The Effectiveness Of Shields
Every ship in Star Trek is fitted with shields to protect them from attack. While there is a huge variety in the strength of these deflectors, they are almost universally present. Star Trek II: The Wrath of Khan features a plot point about conning the Reliant into lowering its shields to allow the Enterprise to even the playing field. Star Trek: Nemesis keeps a running tally of how long is left before the Scimitar gets through the Enterprise-E's defences.
Star Trek: Deep Space Nine features the most offences in this category. As the Dominion War began in earnest, the writers were faced with the challenge of accounting for each ship's shields gradually getting weaker and weaker as the enemy bombardments continued. They came up with a slightly disappointing answer to this, which is to say that Federation shields generally proved to be ineffective against Dominion weapons.
If that was a consistent rule, then it would be more forgivable. However, the Defiant seemed to generally do just fine against Jem'hadar weapons, while Deep Space Nine's shield grid was miraculously strong enough to withhold attack from an entire fleet in Call To Arms. Yet barely six episodes later in the infamous Operation Return, in Sacrifice of Angels, the Dominion are once again cutting through non-existent shield grids and destroying hundreds of Starfleet vessels. Were the sequence not so memorable, it would be slightly more forgivable - yet the visuals are so striking that they are impossible to ignore.