The difference now is that Russia is angry about the strike — and showing it.

Russia has called out Israel publicly, condemned the attack and summoned the Israeli ambassador to “discuss developments.” The alleged strike, which the Israeli government has not acknowledged, came soon after a Syrian chemical weapons attack on civilians. But the two attacks might not be connected.

Here’s a quick rundown of why Israel is bombing Syria, why it officially pretends it isn’t, and why Russia is upset about it.

Israel has attacked Syrian targets many, many times. 

Israel does not like Syria — and it hates Syria’s ally, Iran.

Israel and Syria are technically in a state of war, but have not engaged in sustained armed conflict since the Yom Kippur War in 1973. Instead, the two sides have fought through Syrian-funded proxies like the Lebanese terror group Hezbollah. When the civil war in Syria began in 2011, Israel stayed neutral, providing some humanitarian aid to victims on the border but otherwise remaining out of the fray.

The exception has been Israeli strikes against Syrian weapons convoys en route to Hezbollah. When Syrian President Bashar Assad’s government was at risk of collapse in the past, Israel worried that it would send its most powerful ordnance to Hezbollah, which has a stated aim of destroying Israel.

Now, as Assad is nearing the defeat of the Syrian rebels, Israel is worried that Iran will set up permanent military bases in the country, at Israel’s doorstep. Iran’s leaders have pledged to wipe Israel off the map, and Israeli Prime Minister Benjamin Netanyahu incessantly accuses Iran of seeking to develop nuclear weapons that would existentially threaten Israel.

In February, Israel and Iran engaged in rare direct conflict over Syria: Iran launched a drone from a Syrian base into Israel, and Israel responded by bombing the base. Syria shot down an Israeli plane.

Monday’s Israeli strike targeted the same base as in February, killing 14 people. It came shortly after Assad reportedly murdered at least 40 of his own citizens with chemical weapons, but Israel’s attack does not appear to be in response.

Russia is angry this time. 

Ever since Russia increased its involvement in the civil war in 2015, sending soldiers and materiel to Syria, Israel has tried to stay on Russia’s good side.

That year, the two countries agreed to coordinate military plans over Syria so they would not accidentally attack each other. And Netanyahu has tried to cozy up to President Vladimir Putin in various other ways — publicly thanking Russia for the Soviet Union’s role in defeating the Nazis, and staying silent on Russia’s seizure of Crimea and its invasion of Ukraine.

But Russia-Israel relations have always been fraught. The Soviet Union cut off ties with Israel after the latter’s victory in the 1967 war, re-establishing them only as the Soviet government was collapsing. And today, the two nations find themselves on opposite sides of the international order. Israel is allied with the United States, while Russia is still allied with Syria and Iran, two of Israel’s worst enemies.

Monday’s strike targeted a base where Russian personnel might have been present, and Russia is complaining that it was not told of the strike in advance. So this time it’s not letting Israel’s bombings go unmentioned.

Israel usually keeps quiet about the attacks. 

How many times has Israel attacked Syria since 2012? Few people, if any, know the exact number, so reports have relied on estimates like dozens, scores, even hundreds.

Israel does not want to be seen as supporting one side of the complex conflict or becoming involved directly in the war. When Israeli officials do allude to the strikes, they focus on preventing threats to Israel, not bolstering Assad, the rebels, Islamists or anyone else.

Netanyahu acknowledged these strikes last year. And on Monday, following the strike, he did say “We have one clear and simple rule, and we seek to express it constantly: If someone tries to attack you, rise up and attack him.”