President Trump has hollowed out the federal government, failing to even nominate anyone for 420 of the 599 available political jobs, as of Tuesday afternoon. Only 42 Trump appointees have been officially confirmed by the Senate.

You would expect that Trump would have at least nominated people to fill the positions responsible for issues he claims to care most deeply about, like fighting terrorism and securing the border. You’d be wrong.

The Pentagon has 53 political slots; only six of them have been filled (10 people have been nominated but not yet confirmed). At the Department of Homeland Security, two positions out of 16 have been filled. The State Department has only filled nine of 120 positions. Embassies in key countries like China, Britain, Germany, and India don’t yet have ambassadors.

Some of the open slots are particularly glaring. No one has been appointed to run the Transportation Security Administration, which is primarily charged with protecting the United States’ air travel system. The same goes for Immigration and Customs Enforcement. And then, of course, there’s the FBI, currently in the awkward position of investigating several current and former members of Trump’s campaign and administration. Trump fired James Comey on May 9; it took him about one month to nominate a successor.

That being said, all of Trump’s Cabinet slots have been filled. Still, the lower-level positions responsible for actually running the departments and carrying out day-to-day tasks remain vacant.

“With only secretaries in place, senior leaders in this administration have almost no connectivity to their organizations. At best they are treading water in managing their portfolios, which are really huge and complex,” said Loren DeJonge Schulman, a senior fellow at the Center for a New American Security and a top aide to former National Security Adviser Susan Rice.

And even though most of these positions are temporarily filled by career officials who worked under the Obama administration, there is a limit to what they can accomplish. “Even though we have very talented career officials either in acting roles or doing their day jobs, they are not part of the trusted circle in the Trump administration,” said Schulman. “So if there’s a crisis, they aren’t going to be the first people who are called.”

The government bureaucracy can be a confusing thing to sort through. We’re here to break it down. Below is a guide to the 14 most important national security jobs that are still vacant, why the posts matter, and who the nominees are (if the positions even have nominees).

1) FBI Director

Status: President Trump finally announced his pick for the new FBI director on Twitter last Wednesday morning, weeks after James Comey was fired from the position in May. Trump’s nominee, Christopher A. Wray, still has to be officially nominated and approved by the Senate.

Why it matters: This one is pretty obvious given ongoing investigations into Russian meddling in the 2016 election and the Trump team’s ties with Russia, which would be managed by the FBI director. The FBI director is essentially the top law enforcement official in the country, but having a competent director is even more important now with the ongoing investigations.

Meet the nominee: Wray previously ran the criminal division of the Department of Justice under George W. Bush, but he hasn’t worked within the FBI itself, reported Vox’s Dara Lind. Most recently, he defended New Jersey Gov. Chris Christie following the Bridgegate scandal.

2) Assistant Secretary for Immigration and Customs Enforcement

Status: No nominee, but Thomas Homan is the temporary acting director.

Why it matters: The assistant secretary for ICE represents the agency at wider Homeland Security meetings. ICE enforces any laws related to the border, immigration, and trade. Put simply, it’s the agency that arrests and deports individuals who might be in the US illegally. Trump has spoken aggressively about massively ramping up efforts to deport undocumented immigrants, so it’s surprising he hasn’t nominated anyone for the position in charge of that.

But even without an appointed head of ICE, Trump’s agenda is still being carried out. ICE has already enforced policies that have successfully increased the risk of deportation for millions of immigrants. Trump has also emphasized that he wants immigration agents to have more freedom to make decisions in the field without much oversight from officials in Washington.

3) TSA Administrator

Status: David Pekoske was nominated earlier this week, and his appointment still needs to be confirmed.

Why it matters: The US has imposed a “laptop ban” requiring passengers to check their laptops on flights from 10 airports around the world, and there is talk about expanding it. So the Trump administration appears to believe there are imminent travel threats. The Transportation Security Administration includes roughly 60,000 employees who are responsible for maintaining security in more than 450 airports throughout the US. The head of the TSA manages all employees and works to guarantee that there are no attacks against airports.

Meet the nominee: Pekoske previously worked as second in command and chief operating officer at the Coast Guard, according to a White House release. His position with the Coast Guard was a military post, and since retiring in 2010, he has been working in the private government services industry.

4) Deputy Secretary of Defense

Status: Trump announced his nomination of Patrick Shanahan, but the nomination still needs to be sent to Senate and confirmed.

Why it matters: The DOD deputy secretary is the second-highest-ranking civilian at the Pentagon, runs day-to-day operations for the department, and manages its hundreds of thousands of employees.

Meet the nominee: Shanahan has never worked in the Pentagon or for the military. He is currently a top executive at Boeing, with 30 years of experience at the company. He got the nod after Secretary of Defense Jim Mattis’s top pick, Michèle Flournoy, took herself out of consideration because of broader disagreements with the Trump administration. Flournoy had held the No. 3 slot at the Pentagon during the Obama years and would have been the first woman to hold the deputy position.

5) Undersecretary for Policy for the Pentagon

Status: No nominee, but Robert Karem, former Middle East adviser to Vice President Dick Cheney, is acting in the position.

Why it matters: The undersecretary for policy at the DOD is the third-highest civilian position in the Pentagon. The undersecretary typically represents the DOD at important interagency security meetings, such as the National Security Council Deputies Committee (which prepares policy options for consideration by the president and the more widely known National Security Council). Because this position is not filled, there is a leadership gap in the part of the Pentagon charged with setting coherent policy toward North Korea, China, the anti-ISIS fight, and other complicated issues.

6) Undersecretary for Political Affairs for the State Department

Status: No nominee, but Thomas Shannon, who was confirmed under the Obama administration, continues to work in the role.

Why it matters: The undersecretary for political affairs is the person who represents the State Department when it comes to interagency deliberations and making day-to-day decisions, according to Schulman. Without someone in this position, the State Department’s voice would be absent from conversations occurring between agencies in times of crisis. Of course, Thomas Shannon is currently acting in that role, but since he was confirmed under the Obama administration, his recommendations might not be given as much weight as they would if he were a Trump nominee.

7) Assistant Secretary for Diplomatic Security for the State Department

Status: No nominee, but Bill Miller, a holdover from the Obama administration, is currently acting in the position.

Why it matters: Remember how Trump and his fellow Republicans spent years criticizing Hillary Clinton for the deadly 2012 attack on a US compound in Benghazi, Libya? Well, Trump still hasn’t even nominated someone who would oversee all diplomatic security abroad, including securing embassies and maintaining the safety of foreign service officers and other State employees. Trump has proposed a huge cut in the State Department’s budget, but embassy security would be maintained — Foreign Policy reported that in Trump’s proposed budget, $2.2 billion would be spent on new embassy construction and maintenance in 2018.

8) Ambassador to the UK

Status: Trump informally nominated Robert “Woody” Johnson, the wealthy owner of the NFL’s New York Jets, but he still has not sent Johnson’s nomination to Senate.

Why it matters: Ambassadors represent the United States when crisis strikes abroad. When terrorists attacked London last week, the top US diplomat there was Lewis Lukens, a career official who previously served in China and Australia and worked with Hillary Clinton when she was secretary of state. That made it harder for the State Department to tamp down British fury over Trump’s tweets inaccurately criticizing London Mayor Sadiq Khan and calling for support of his travel ban.

Meet the nominee: Johnson is a billionaire who donated hundreds of thousands of dollars to the GOP and a joint fundraising committee for Trump.

9) Ambassador to China

Status: The acting ambassador resigned from his post last week after saying he couldn’t support Trump’s decision to withdraw from the Paris climate agreement. Former Iowa Gov. Terry Branstad was confirmed in late May but still has not taken up his post in Beijing.

Why it matters: North Korea launched its fourth missile test in a month on Thursday. The South Korean president just halted construction of THAAD, a US-provided missile defense system. China looms over that security crisis, as it does over most issues in Asia. With the administration still hashing out its free trade policies, the White House also needs someone in Beijing to help work through some of the most complex issues facing the US-China relationship.

Meet the nominee: Branstad was the longest-serving governor in the US, according to the Washington Post. He’s apparently “old friends” with Chinese President Xi Jinping, and the two get along fairly well, according to the same Post article. (They’ve actually been friends since 1985, when Xi visited Iowa to learn about corn, pork, and soybean trading opportunities.) Both Republicans and Democrats applauded Branstad’s performance during his confirmation hearing in May, saying his friendship with Xi could bode well for US-China relations.

10) US Representative to NATO

Status: No nominee, but the previous representative, Earle Litzenberger, is still performing the duties.

Why it matters: Given Trump’s history of criticizing the organization responsible for countering Russia and maintaining peace in the region (he once called it “obsolete”), it might be difficult to find someone willing to take the job. The NATO ambassador sits on the North Atlantic Council, the committee that makes decisions about military involvement and votes on behalf of the US. Typically, the diplomat holding the position votes according to what the president and other top officials advise. But because the position is still vacant, the US’s voice is missing at the table.

11) Undersecretary for Intelligence and Analysis for the Department of Homeland Security

Status: David Glawe was nominated in March but has not been confirmed yet.

Why it matters: This position is essentially the Department of Homeland Security’s head of intelligence — a big deal. The office is responsible for gathering information on potential threats to domestic security from both government and nongovernment sources. It is the only organization within the intelligence community that also shares that information with state and local governments, private organizations, and other entities outside of the federal government.

Meet the nominee: Glawe has worked in many areas of intelligence, including US Customs and Border Protection, the Office of the Director of National Intelligence, the FBI, and the Postal Inspection Service. He also worked as a police officer in Houston.

12) Assistant Attorney General for the National Security Division for the Department of Justice

Status: No nominee, but Dana Boente was named acting assistant attorney general this past April. He was nominated in 2015 by the Obama administration to serve as US attorney for the Eastern District of Virginia and has worked for the Department of Justice for more than 30 years.

Why it matters: The National Security Division is one of the most important divisions in the Justice Department. Its mission is to protect national security, and it has done just that by filing charges against Russian and Chinese hackers and investigating Americans inspired by ISIS and other terrorist organizations, according to NPR. Most recently, the assistant AG has been leading the department’s investigation into possible Russian involvement in the 2016 election and the Trump team’s ties to Russia.

13) Assistant Attorney General for the Justice Department’s Office of Legal Counsel

Status: Steven Engel was nominated and is waiting to be confirmed by the Senate.

Why it matters: The Office of Legal Counsel provides legal advice to the president and all Cabinet departments. It is also meant to review all pending executive orders, which means the catastrophic travel ban gaffe could potentially have been avoided with a strong lawyer in the post.

Meet the nominee: Engel most recently worked for a private law firm, but he previously worked for the DOJ Office of Legal Counsel as the deputy assistant attorney general during the Bush years.

14) FEMA Administrator

Status: In late April, Trump nominated Brock Long. Long has yet to be confirmed.

Why it matters: Hurricane season is here, and researchers are expecting more storms than normal — at least 14 major ones, to be exact. On top of that, there are wildfires, tornadoes, and other disasters expected to hit throughout the US this summer. FEMA, the Federal Emergency Management Agency, responds whenever major disasters strike, and the administrator leads that response. Without a leader, FEMA may be disorganized and slower to respond.

Meet the nominee: Long definitely has experience when it comes to emergency management. He led the Alabama Emergency Management Agency from 2008 to 2011 and currently works for an emergency management firm based in Illinois, according to the New York Times.